For me getting started I sort of had the benefit of knowing there were haters/doubters/uninformed well meaning folks out there on the System, so when I'd scout out a school I would be upfront and say I was a fan, but that I was also looking to explore all perspectives and views on grappling (some instructors will tend to relax when you present it that way so that they don't feel like you're the kid who comes to class and half heartedly goes through drills so that you can get to rolling and try to hit another electric chair or truck on the other students).
When I went to class if it was nogi I would wear a generic rashguard, I would have my 10th Planet patch on the shorts but I wouldn't try to come across as "only wanting to do 10thpjj techs". Once I got comfortable with a school or club that I was visiting I would then wear my mix of 10thpjj rashguards and start to open up with lockdown truck more. I think once you establish yourself that way even the naysayers will give you some room to work with and actually watch to see if you're able to make the moves work for you.
With regards to the higher belt who got upset with you, I'll give him the benefit of the doubt and say he might've had a bad day prior going in, and then having you (a lower blood oh no!) pass his guard with the sweep and take top may have just him off, and/or maybe he's heard the stereotypes on lockdown or stoner control being tough on the knees (perhaps he had a prior injury, or maybe is just a bit older and trying to watch his health). I personally think if he had something to say it would've been better served in private to you instead of in the open during class based on what I read.
Either way, at the end of the day you're a student and customer at the school too, and you have a right (as long as it doesn't hurt anyone) to discover your path, and if there are higher belts or students who can't accept that then maybe they just aren't folks you want to be rolling with at least in the short term until they cool down. I think one other benefit I've had is the wide array of clubs and schools I'm able to visit, so if things ever get heated at one place (which is rare) I can always visit the other place or two to gt fresh exposure to other teammates and let things cool down.
Hope that helps a bit, keep the faith in the system, don't limit your perspectives, and I think one day you'll have your moment to shine on the big stage too