The tweet literally said "OU players fake punching Mixon". Aside from the chin-scratching emoji, it's a pretty objective title.
The Oklahoma teammates did in fact make punching gestures that obviously didn't hurt. The text of the tweet is factual. The emoji is likely someone who is implying, "Eehhh not a great look."
I've seen a lot of football over the years, meaning I've seen a lot of celebrations. Unless we're talking macho 80's and karate-obsessed 90's, I haven't really seen a whole bunch of fake fighting as a means of celebration. Head(helmet)butts and taps, buttslaps, sure. Punching gestures to the facemask and torso, not so much.
If this was premeditated, it's most likely that this is just a misguided "I stand by my teammate" statement, through the sense of humor of young men that haven't learned everything the world has to teach them. If it wasn't premeditated, maybe this is just an opportune time to grow some self-awareness.
Of course because it's twitter and this is an issue where there's gonna be no grand, sweeping resolution between unnecessary violence and second chances. Also, the public is too bored and will analyze too quickly how irrelevant things make them feel. So enjoy the spat, and thank lord it's Oklahoma and not Tennessee.