Probably people act shocked because of how much you trash a thing they like.

Telling people that a thing they like is equivalent to "wet grains that have been fermenting in wet newspapers that have been next to a vat of raccoon piss" is going to offend people. By so dramatically demonstrating your huge disdain, in so far as to create new creative ways to describe how bad it is, it implies that the person who likes it is making a bad choice/has bad taste/is otherwise an idiot.

People likely aren't offended that you don't like beer, they are likely offended by the way you are treating them.