First of all, I am not a Roman Catholic, but do know many, many Roman Catholics who are Christians.
As for many Calvinists on FR, they hold to all five points of TULIP; including double predestination. In other words, they believe that prior to the creation, God specifically determined exactly who was going to heaven and who was going to hell and there is no decision or choice than can be made by that individual to alter their fate.
In fact there was one FReeper Hyper-Calvinist who stated on her Freeper home page that Billy Graham preacher a false Gospel because Graham preached that a man determines his destination by the choice he makes about Jesus in this life.
Reformed theology has a much wider history and dynamic than what people on FR say. I'm sure many are right and many are wrong. I'm more concerned about the theology iin general or, if you want to get more specific, what the Bible has to say about God's role in salvation.
Knowing that salvation is God's gift and as Jesus said "I've them eternal life, and they shall never perish; no one can snatch them out of my hand" brings amazing assurance to the believer and this is my main concern.
as I said, the problem may be that the hyper-Calvinists are the most vocal — or even “were”. Unfortunately that means the information we received 2008-2010 made us (at least me) believe that all were of that bent of mind — indeed I was told that was so and to be otherwise was not to be Calvinist.