Too many things people say are "just because I think so" without much thinking going into why or how they came to that conclusion. So, maybe calling out baselessly opinionated people is ok?
As an aside, seems like the response was in the same tone as the parent's comment.
>So, maybe calling out baselessly opinionated people is ok?
Of course it's okay. But call them out by saying they're wrong/baseless/uninformed, not by dismissing their "right to an opinion".
And, in such cases, I don't think people can be allowed hide behind the "right to an opinion". If you think about it, this is the source of "alternate facts".
But, hey, that's just my opinion :)