The Scriptures incourage Christians to judge false converts and false doctrine.
15: Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.
16: Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles?
17: Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.
18: A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit.
19: Every tree that bringeth not forth good fruit is hewn down, and cast into the fire.
20: Wherefore by their fruits ye shall know them.
I can judge Obama by his doctrine, by his actions, and by the company he keeps.