I dump out portions of a lot of commercial beers as well. In PA the only way to buy beer is by the case. I have a place that does sampler cases. 24 different brews of a similar style. I buy these cases on occasion. Generally most are good, some are decent enough to drink and a few are sink worthy.
I bought a Winter Warmer case recently and there are , unfortunately, more beers that I don't like than normal. I have dumped out maybe 5 so far out of 18.
I have absolutely no problem with dumping a beer I don't like. The sooner it is gone the sooner I can be drinking a beer I like (and I ALWAYS have tens of cases of beer that I love on hand) and life is way too short to drink bad beer.