While I sympathize with the family and think the church is being a bit cold I think that if he honestly is a possible danger and is highly disruptive then he should probably be kept at home. Instead the family should talk with their priest about possibly doing an in-home visit once or twice a week for communion, bible study, etc., so the family will still be able to participate with the church without everyone else feeling uncomfortable, endangered, or whatever.
There's other ways to worship besides inside the church itself. The family should probably try to explore those options.