Mod advice on Rule #1

The comments in today's Sublime post exemplify the issue our Mods face.

We want to live Rule #1: BE POSITIVE here and create a place for people to share music and their artists.

OP contributed to the sub, only to get comments and downvoted. Do you think he'll contribute again?

For example, "I don't care for Sublime's direction" seems OK, but calling Sublime a "sell-out" seems over the line and should warrant a warning reply. Repeated activity would warrant an official Reddit warning, then a temporary ban, then a perm ban.

Is this the right approach?

IF we're wrong on this, please say WHY. We are genuinely trying to get the mix right. Stay Positive = Rule #1