If my students were only posting cat videos, I wouldn't have a problem with people clicking "like" as cat videos lend themselves to that behavior. On the other hand, because most of the posts were intended to start a discussion or get feedback clicking "Like" is less useful, in fact it's often meaningless.
Before Facebook and Twitter, if you wanted to engage with somebody's post, the only way (on nearly all platforms) was to make a comment. Writing and posting a comment takes at least a little thought and effort.
I'm not saying that "Liking" is bad and everyone should stop it. What I am saying is this: think about what your "like" means.
Here's an example of a post where "liking" would be completely appropriate:
In this case, "like" simply means "yes."
On the other hand, think about what "like" means for a post like this:
In this case, "like" doesn't mean much of anything, except maybe "I approve of this idea, but don't want to contribute anything to it."
What do you think?