It’s a balance.
Yes
The flip side is yeshivos who kick out kids all the time–essentially guaranteeing they will go off the derech–on the safeik that they might negatively influence someone.
I am not aware of any yeshivos which routinely kick kids out “all the time”. In the rare cases where kids are kicked out, the negative influence is usually karov l’vaday. Perhaps you are, and then they’re wrong. There is a huge difference, though, between expelling a kid and having a strict acceptance policy. A school is allowed to create an identity for itself. There is also a big difference between situations where there are other options or where there aren’t.
It’s very selfish attitude. You might ask what tenets of chareidi’ism provide that you are supposed to value any amount of risk to your own over any amount of damage to another. I’m not aware of any teaching in the Torah like that, so it must come from outside influences.
Chayecha kodmin. (Please take that in the context if what I wrote above.)