if they are validly baptized, they are Catholic...
And just what is a "valid" baptism??
People who attack Catholicism and the Catholic Church but claim to be Christian are one thing, those who are sincere but who due to a wide variety of circumstances haven't yet come to understand that there is only One True Church are another. You can see this from what Christ Himself says in Luke Chapter 9.
Luke 9:49 And John, answering, said : Master, we saw a certain man casting out devils in thy name, and we forbade him, because he followeth not with us. Luke 9:50 And Jesus said to him : Forbid him not ; for he that is not against you, is for you.