MAking rules against liking airsoft guns has no basis, and is a violation of a laundry list of rights.
Constitutional rights don't exist in school. You can get suspended for anything. Free speech doesn't exist there. Colleges can also discipline people for what they do on campus. Going to college is a privilege, not a Constitutional right. But if people do things in their private life, obviously they can't be disciplined by their school or college. If they post something on the Internet from home and then access that post in the classroom, you could say they could be disciplined. If people are concerned, then they should keep their private life separate from their academic life.
I have experience with the issue. In 10th Grade, I drew a picture of Cartman from South Park dressed in his Hitler Halloween costume and they suspended me for a day when the teacher saw it. The teacher knew I'm Jewish but I still got suspended. Someone could actually draw a picture of Hitler and curse him on it and they would still suspend you. If you draw a picture of an Arab dressed up as a Nazi, you would also get suspended. You can also get suspended for expressing political views if it offends another student. In 12th Grade, I insulted some stupid twins by calling them "stupid Palestinians" and the teacher the principal said not to offend their heritage, even though the twins in question were the daughters of a self-hating Jew who married an Israeli Arab and they claim to be Fakestinian Muslims. They belong to the same heritage as me (Jewish) but they are traitors and identify with their Arab Muslim father. They also admitted that their father is from an Egyptian background like most Fakestinians. In college, I saw them a few times and they were wearing the Muslim head covering and they said they spent time in the "West Bank" with Fakestinian family members.