What about publicly sharing positive personal reaction, is that okay? If you answer yes to that and no to the other then you've got a problem on your hands.
You're worried about the world being too kind and positive? You shouldn't. There are enough people actually doing things worthy of scorn -- enough to wear out your keyboard -- without besmirching someone for the flimsiest of reasons.
Furthermore it induced a few interesting replies about his style of looking directly into the camera and long-takes, and parasocial relationships (to be fair, it also induced a single reply with someone implying that while Mr. Rogers probably isn't a pedophile, "better safe than sorry").
As an aside, I'm somewhat surprised nobody's mentioned the puppets yet; lots of people find puppets creepy.
That’s pretty passive aggressive. Wouldn’t you be offended if someone said that about you? “I never said you were stupid, I just /think/ of you as stupid.”
Secondly, we are talking about a performer while performing[1] Sharing personal reactions (both positive and negative) to public performances is, IMO, well within the bounds of polite discourse.
1: This is harder to distinguish when the actor's name is "Fred Rogers" and the role is "Mr. Rogers," but the original comment referred to "Mr. Rogers" rather than Fred Rogers and used the phrase "especially while singing," so I think it's a safe assumption here.