Sorry for not using the right words. I still think "who does not praying for a non-Catholic serve?" It doesn't do anything to God, but everything to that soul and that serves the devil. So there is something wrong.
There are other examples, but I picture a Muslim who got caught and killed right after he just raped and cut off the girl's head. Now there is a guy that I personally believe to be in hell. Aside from possibly saying to myself - "May God have mercy on his soul," we should not pray for that guy.
Now if a devoted baptist preacher were to die during his sermon, we do not pray for him because we are certain he died outside of the Church. On that account and per the dogma, we know that man has no hope of salvation, which is the reason that we do not pray for him.