I don't really agree with some of your assumptions. At many companies, many of the people also are evil. Many people who hold shares and public office are also evil.
I don't think it's necessary to conclude that because a company is evil then everyone who works at the company is evil. But it's sort of like the evilness of the company is a weighted function of the evilness of the people who control it. Someone with a small role may be relatively good while the company overall can still be evil. Someone who merely uses the company's products is even more removed from the company's own level of evil. If the company is evil it usually means there is some relatively small group of people in control of it making evil decisions.
Now, I'm using phraseology here like "is evil" as a shorthand for "takes actions that are evil". The overall level of evilness or goodness of a person is an aggregate of their actions. So a person who works for an evil company or buys an evil company's products "is evil", but only insofar as they do so. I don't think this is even particularly controversial, except insofar as people may prefer alternative terms like "immoral" or "unethical" rather than "evil". It's clear people disagree about which acts or companies are evil, but I think relatively few people view all association with all companies totally neutrally.
I do agree with you that taking personal responsibility is a good step. And, I mean, I think people do that too. All kinds of people avoid buying from certain companies, or buy SRI funds or whatever, for various ethically-based reasons.
However, I don't entirely agree with the view that says it's useless or hypocritical to claim that reform is necessary unless you are going to "do something". Yes, on some level we need to "do something", but saying that something needs to be done is itself doing something. I think the idea that change has to be preceded or built from "saintly" grassroots actions is a pernicious myth that demotivates people from seeking large-scale change. My slogan for this is "Big problems require big solutions".
This means that it's unhelpful to say that, e.g., everyone who wants regulation of activities that Company X does has to first purge themselves of all association with Company X. In many cases a system arises which makes such purges difficult or impossible. As an extreme, if someone lives in an area with few places to get food, they may be forced to patronize a grocery store even if they know that company is evil. Part of "big solutions" means replacing the bad ways of doing things with new things, rather than saying that we first have to get rid of the bad things to get some kind of clean slate before we can build new good things.