Major
Footballguy
Some are worse than others but if you go (especially in NY or Boston), just don't wear any team merchandise. I wore an Astros hat at Yankee Stadium (2017 ALCS) knowing the #### storm it would cause. I took some solace because the seats were good and that I could take the hat off at anytime. If you're in the bleachers, you don't have much value for your life. After the first few innings and the struggle just to wait out the concession line, I never left my seat and I sure as hell took it off after the game on the subway ride home.I can't imagine going to a playoff game in the opposing teams stadium. If your team loses, you'll be ridiculed relentlessly. And if they win, I'd be afraid of angry drunks looking to exact some revenge. Lose-lose.
In Houston, the fans are pretty friendly and non confrontational. You'll get some gentle teasing or the occasional drunk talking smack but that's about it. I'd think National fans would be somewhere in between Houston and Boston. You'll be fine Sheik.