There's four basic things I look for: bias, reach, intensity, and goal.

    Sometimes a company gets in the news for supporting something I find reprehensible, but it turns out that they're basically throwing money at all sides or at least a lot of sides. As noxious as it may be, standard operating procedure for most corportations is to donate to everyone with a shot at winning on an issue, so as to have some hooks in whoever wins. Unless the other factors below rise to truly epic levels, I'm not going to get too worked up by a corporation supporting something or someone I dislike if they're just throwing money around.

    The most common sort of bias, of course, is party-line. A lot of companies only give money to Republican candidates and causes, or only Democratic. While this annoys me a little, it's nothing special.

    Some companies have a pet issue they always seem to be throwing money at. Maybe they're big union-busters, or promote a particular religious viewpoint, or have a single Amendment in the Bill of Rights that they promote at the expense of all others. That level of bias is more likely to raise my hackles, even if I tend to agree with them. Because now they're trying to subvert democracy by swinging their golden club around.

    It's important to consider how wide an impact the company wants to have. This is a pretty simple category to consider: if the company only wants to control what they themselves have to do (i.e. they don't want to allow unions, they close on Sundays for religious reasons, they don't want to provide insurance for their employees) it's not nearly as bad as if they want to change how things work for everyone (weaken unions in general, forbid anyone from doing business on Sundays, strike down the Affordable Care Act).

    While I'm less likely to give my business to a company that insists on mistreating its employees, my minimal faith in the Free Market suggests that such behavior will eventually backfire on the company and they'll have to stop treating their employees badly if they want to be competitive. But when a company decides to use their economic clout to change the rights of people not part of the company...that's crossing a line.

    How much is the company doing to push its political goals? If all they're doing is giving money to candidates, I'm not going to get too worked up about it. Money in politics is a blight, but it's sort of the baseline of horrible right now. A company that gives a lot of money to a candidate I despise will still probably get my reluctant business.

    Running issues ads or giving money to organizations that advocate things that no candidate would be able to get away with takes it to the next level (i.e. as racist as a candidate may be in their policies, they'll rarely come out and say that stuff, but if the company gives money to the KKK it's a definite reason to boycott).

    Probably the highest level of intensity involves trying to write or strike down the laws directly. There's companies and organizations that pay very clever people to write laws that can sneak past the usual objections and get enacted, such as voter ID laws that don't look like they discriminate against certain groups but do so via subtle statistical effects. And then there's lawsuit hunting, where a company will provide legal teams for anyone who wants to sue to overturn a law the company doesn't like but has no standing on themselves.

    Of course, all of the above assumes that the company is trying to do something I dislike...if they're doing something I like, I may be annoyed at the perversion of democracy, but probably not enough to boycott. So, what sort of goals do I dislike?

    Now, obviously nothing about society is going to be linear. If you give too many rights to the weak it can cause things to break down. If you financially help the weak too much, the strong become weak. And so forth. But right now, I don't think we're in danger of flipping over to the bad side of those curves.

    Majority groups (heterosexuals, whites, cisgendered people) are strong. Minority groups that benefit from historical privilege (men, Christians, native-born) are strong. The rich are a tiny minority that is always strong. If a company's political goals have the effect of strengthening the strong and weakening the weak, I'm going to be a lot more likely to find them reprehensible than if I think the company is going overboard in trying to strengthen the weak. Especially if the company tries to act like a privileged group is a persecuted minority in need of protection.

    So, I've determined that a company is Wrong and should not get my money. Can I actually boycott them? Depends. The Walton family is pretty vile on most of my meters (not all of them, IIRC, but most) and corporate policies basically drain money from the poor and stuff it in the company's pockets. But not shopping at Walmart at all isn't really practical. I try to buy elsewhere as much as I can, but Walmart has sewn up so much of the retail space even in cities (never mind the small towns I've lived in) that I can't avoid it.

    On the other extreme, I can't boycott a company I never did business with. Oh, I can be smug about avoiding Chik-fil-A if I want, and badmouth them online, but long before they started being visibly horrible I determined I didn't really like their food.

    That leaves a middle ground of companies whose products or services I do like, but can do without. I like Papa Johns pizza, but will no longer buy it on the rare occasion I order pizza for delivery. I like Barilla pasta, but it's easy to avoid them and so it didn't take much corporate jerkitude on their part to get me to stop. Hobby Lobby has a lot of stuff I want to buy, but for a few years I stopped buying from them entirely...and even now, it's only with a 40% off coupon and only if no one else has what I'm looking for (and if it's not a Sunday, obviously).

    I try to avoid holding grudges, so if it looks like a company has stopped doing something I dislike, I ease back on any boycotts. Usually. Sometimes, though, I find I get by okay without their product or service, so while I may not be boycotting them per se, I no longer have the habit of giving them my money. (For instance, Barilla hasn't been in the news for years, but I've found other brands I like and see no reason to go back.)