Yes, anything can be used as a weapon by someone who's determined enough. And there will always be crazies.

We can either ban literally everything, on the grounds that it could be dangerous, and live in a surveillance state with predictive policing, imprisoning people who haven't committed any crimes just because an algorithm said that they might, all to try to eliminate crime completely and bring statistics down to zero; or we can accept that there's always some risk to living a life, we can be prepared by learning how to defend ourselves (and living in a society that permits us to defend ourselves when necessary), we can take care of each other by standing up for what's right and not tolerating hatred and extremism, and we can provide robust social programs to get people the mental health treatment that they need and help them integrate into society rather than stigmatizing them and ostracizing them, driving them further into isolation and delusion, and occasionally locking them up extrajudicially under the guise of a "mental health hold", without actually providing them with any effective treatments or paths forward beyond the bare minimum necessary to appear on paper as if you did your job, solely for the courts, to avoid lawsuits, and without any regard for the wellbeing of the patient.

There's a lot we can do to make society a safer place, but unfortunately there will always be some element of risk, and trying to eliminate that completely isn't even desirable. You either live with a risk of danger, or with guaranteed oppression (and still have a risk of danger!).