The mere fact anyone claims salvation can be lost.
1. States God is not powerful enough to do what he promised (finish the work he started until the day of Christ)
2. States God is a liar (he did not perfect forever those who are being sanctified, if he did, then they are saved forever)
3. States Gods promises are not reliable (Jesus said whoever trusted in him will never hunger, never thirst, Never die, Live forever, and given his ASSURANCE he will raise them from the dead)
4. States God makes mistakes (he gave eternal life to someone he knew he would have to take back. because of sin, lack of faith or whatever reason one gives for why the eternal life will be surrendered)
States Gods pledge is meaningless (he said he gave the seal until the day of redemption. And never said he would take it back for any reason)
5. States we are more powerful than God (we can pluck ourselves out of his hands)
6. States eternal life is not eternal, but conditional.
About the only form which I would try not to argue about much is the form which says a person who Denys Christ lost salvation. Because no one believes and antichrist is saved, (however, I would not judge them, because I do not know their Heart, only God does (the one who says they deny Christ, peter denied Christ, and Christ never asked him to repent)
Al the rest, They slander us and say we love sin, They say we hate works, We condemn anyone who teaches works will be done by Gods children.. Yet get angry when we question what their faith is truly in.. and try to tell them we think they offend God and his character by their very belief.
So it is ok for them to judge, but how dare us say what we think..
Sadly, it has been going on since the beginning of the church, and it will go on until Christ returns.