I also don't see what's "better" about being a multishipper. To me that just means waffling.

I totally agree. Although sometimes I understand when someone really likes a certain character but not that character's canon ship(s). That makes more sense to me, but yeah, it just seems like waffling or not wanting to take a stand and risk being criticized.

Also--there's always a lot of scolding should you express your strong dislike for a character, which I also don't understand.

This really bugs me too. It's ok to not like characters. They are not real! And they can be disliked for totally reasonable reasons too. And sometimes you can even learn something by talking about why you (or someone) else dislikes a character instead of just getting our nose out of joint.

Not that I haven't gotten my nose out joint plenty.

I also admit to liking difficult characters instead of their easier counterparts. ;)