Very reasonable.
We are not talking about the US and our laws. We are discussing the laws in Israel amongst the Jewish people. I also recognize the men being attacked are also devoted to a faith in God by the obedience to the law they study. That law includes their separation from any woman other than their wife. I suspect it goes quite a bit deeper than that simple observation. The custom respected their faith. Had the woman felt that deeply about sitting in front, perhaps she could also be as cordial to discuss her perspective rather than forcing her actions upon them, assaulting them both physically, soulishly and intentionally to disrupt their spirituality.
IMHO, she would have been better served to work through legitimate authority rather than assuming she could unilaterally force others into her will. The burden was upon her, not upon them.
Now with respect to their actions, one might assert the same, that they also could appeal to legitimate authority to remove her from her location. I suspect in their faith, they had legitimate authority to remove her, but then the issue becomes one of state vs that flavor of Jewish tradition.
I suspect the Jewish gents wouldn't be as offended to sit elsewhere on the bus provided they weren't forced to intermingle with women. I also don't see anything at all wrong with a foreign body of people, a separate nation from the US, having their own laws which fit their people. I do see errors in even Americans foisting our law on foreigners in their lands.