I generally don't just dislike channels; if I find something about the channel not to my liking, I simply discontinue watching that channel.
I can understand why many people dislike PewDiePie.
His humour and comedy is often OTT, and some may not be a fan of the profanity-spewing nature of the guy... Since my type of humour is more or less OTT as well, I can relate.
A comment was made about Markiplier as well.
I suppose I can understand why. He's an entertainer while playing his walkthroughs, so some may not like him either as he can get loud. When I first started watching him, I was on the fence about his content - to a point where I actually almost stopped watching the first LP of him I saw, but I figured, maybe I'll get used to it, and sure enough - I did. He's now one of my favourite Let's Play(ers) on YT.