1. If they use a lot of words without actually sating anything.
2. If what they are sayign is more dogmatic/opinion than it is factual.

We're all different. Thus our responses will be all different as well. That's what keeps things interesting !
Like the rest of life, there are things I like, and things I don't like.
I see no point in harping on reasons I might not like something - it's of little consequence.
I don't have to like everything.
And it's ok. <grin>

I dislike there post.
It doesn’t make me feel any particular way.
I find it boring.
No reason whatsoever.

If ignorant or morally offensive.

If I think someone took time to seriously consider the topic, even if I disagree, or if they make a clever joke, that's good enough for me. But, as you said, if it's unrelated or an attempt at trolling then I'm less inclined to "like."

Oooh... im still new here. I guess i would say nothing. To fight back would be to surrender to them.

I tend to only 'Like' posts that are above and beyond a simple response. There are plenty of responses I agree with, but they just don't seem to add anything more than basically saying 'Yeah, I agree with you' or are just very simplistic. I agree with MsOliver, more options of response buttons would be nice to have. But like with Facebook and other sites, you start getting some confusion sometimes. Especially when someone posts and article or story. Are you 'Likeing' the story content or simply appreciate the person posted a story for people to read, even though it's content is something most people would more likely frown upon. Maybe that's why I have grown to be less reactive to posts in general unless they really make a significant impression. Unless it's a picture of some crazy cat antics! As much as I dislike the negative impacts of cats on the environment, I still love them.