First - I'm sure I have some bias. I'm OK with that.
Second - I think the tweet is dumb. But I'm not up in arms about it. It just comes across as something I would expect from a fan and not the HC. I could see it coming from the student section twitter, the anonymous program twitter, etc., and it wouldn't carry the same weight as coming specifically from an identified head coach.
Similar to the "9 is coming" that KW's twitter feed put out a couple of years ago prior to the rivalry game - it just screams of locker room material and smack talk. And it sounds different if it's a quote in the moment versus a posted tweet. Frankly, I think it's different to say something about what your team did well in a post game press conference - and mention 28 unanswered points. I just see the direct post to twitter as different.
But that's just me.