The first thing you need to keep in mind is that your parents may never approve and support you on this and if that is the case I am truly sorry. On the upside their are some wonderful kids and parents involved in cheer that will be there for you in some capacity.
Based on reactions when cp started doing rec many years ago I will take a guess that your parents, mainly dad, may be afraid of you being gay for liking what is now considered a woman's sport. For some that fear may never go away even though that is not how it works.
I agree with trying to get them to watch some videos of Navarro, Louisville, Kentucky, TGLC, BSB to see the roles the guys play in this. Also, look for videos from Stuntfest this weekend from the college NCA in Daytona this weekend. One thing cp always told people is look at all the beautiful ladies I get to hang out with. It did quiet a lot of them down.
Do a little research on the history of cheer as well. A lot of people are shocked to learn that sideline cheer was originally created by men and dominated by them for many years before women started. Lots of famous men have participated in cheer over the years.
**Sometimes I ask questions I already know the answer to so I feel smart answering them**