I went to the Wikipedia and looked up mass murderers. They have lists of shooters by hate crime, workplace shootings, school shootings, slaughter of families. Based on the names of the killers in the US, it looks like the Ft Hood shooter was the only one that was a Muslim. So if I call for special attention to be paid to Muslims as potential spree shooters, what does that make me?
Tim McVeigh was a Roman Catholic. I didn't hear a whole lot of talk about screening Catholics after he blew up a building. After all, there have been lots of Irish Catholic terrorists, mostly in Ulster, so the Oklahoma City bombing could have been seen as par for the course. Why wasn't it?
Eric Rudolph also identified himself as a Roman Catholic. When he murdered folks based on his religious beliefs there was no call to monitor Catholics. Why not?