Cognitive dissonance is required in order to make it through life, and figuring out where to apply it is very difficult.

I personally became vegetarian not because I changed my mind about the morality of eating meat, but because I started to actually try to be a good person.

It really is not easy, though. Try to go through your day, thinking about all of the impacts of things you do. Your car burning oil, your purchasing decisions enabling megacorporations to take over, your rent propping up a rich person, and so on.

Life just isn't possible if you try to 'do no evil'. So we make up reasons why things are OK, we get lazy, or we just don't think about it beyond the directly terrible acts.

For me, being vegetarian was something that required very little change in my life. You just pick up tofu or other substitutes and go on as usual. Much easier than say, abstaining from capitalism.