The Catholic Beer Reviews writes on the Politics of Beer. He covers some controversies in recent years where beer companies were involved in supporting some evil. For example the Miller Brewing Company and their homosexual advocacy, Samuel Adams with their "Sex for Sam" debacle several years ago, and Sierra Nevada Brewing Company for their support of abortion.
He then "raises the much larger question of a Catholic consumer’s responsibility in the face of corporate behavior that runs directly counter to Catholic moral teaching."
To me this would seem to be in the category of remote material cooperation and so it would not be directly sinful to drink their products responsibly. That is unless you specifically like their support of some evil and then it would be formal material cooperation.
Now my taste buds think that drinking Miller beer would be sinful, so I couldn’t boycott them anyway. Samuel Adam appears not to have made the same mistakes they did previously and so I don’t think their is any real need for a boycott against them. Sierra Nevada is another story and I will be boycotting them. They support as Jeff Culbreath previous wrote one of "Chico’s most notorious abortion providers" and the letter they replied to him with doesn’t change matters. This is too bad since I really like Sierra Nevada’s brews and ironically started buying their beer after Greg Willits of Rosary Army mentioned them.
I will be though looking for Summit Brewing Company’s beers since it is run by a pro-life Catholic convert and Catholic Beer Review recommends them as top notch.
I do hope I never find a reason to have to boycott Guinness.