We cant be sure theyre a son of perdition, thouhg they may act as one, remember saul of tarsus ? Who more sought to destroy the faith than he ? Gal 1:23Folks, this wanna-be resident scholar who prides himself as the smartest man in room just proved that he's a son of perdition since all the offspring of Satan are continuously bent on destroying what God builds, e.g. His Church (1Pet 5:8; Jn 10:10). (Like father, like son!) This truth, though, sadly is never obvious to the self-deceived; for unawareness is the by-product of self-deception.
But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed.
So the most we can say is they act like one at the present time, but who knows, as saul was, he may be a vessel of mercy yet unconverted.