We can easily know who someone is through his actions.
For example, if a man is beating a wood block towards a Buddha statute repeating the name of Amitabha, he must be a Buddhist. Even though he does not mention his religion, we can recognize that he is a Buddhist by his actions.
And if some people gather in a specific place on Friday afternoon and bow down to Mecca, who are they? They are Muslims. Although they do not explain what religion they have, we can know they are Muslims by considering their actions.
He said to me, “Do you see this, son of man? You will see things that are even more detestable than this.” He then brought me into the inner court of the house of the LORD, and there at the entrance to the temple, between the portico and the altar, were about twenty-five men. With their backs toward the temple of the LORD and their faces toward the east, they were bowing down to the sun in the east. (Ezekiel 8:15-16)
People worship sun god within the house of God where they have to give praise to and worship God. Such things are detestable to God. Those who participate in the sun god worship rituals are sun-god worshipers, not God’s children. Their behaviors prove it.