While I understand he's just trash-talking and trying to hype the any upcoming battles, I hate to see talk like that because it drives a wedge between the two communities. Injustice is an enormous opportunity to bring fans of all different kinds of fighters together, and let's face it, NRS desperately needs the embrace of non-MK fans.
If I look on youtube for tutorials, guides, and combos, all I have to do is type "umvc3" and I get more videos than I could watch in a lifetime. However, if I type in "MK9", it's very difficult to find a video that isn't just some guy beating ladder on Expert, a fatality compilation, or a 360p tournament vid from over a year ago. Bringing these communities together will result in a lot more widespread research and release of Injustice tech, which will help new players get better acclimated and pro players discover deeper tech quicker.
That said, I didn't like the way Champ was dissing my community, so here's a quick vid of him getting absolutely bodied at Canada Cup 2012. I mean straight-up destroyed. Enjoy!