Run for myself

My co-worker is so smart. I was deeply impressed with his job. So I told him "You are so smart." And he replied to me "It's rude of you to say such a silly thing." I didn't know whay he meant, so I recomfirmed him what it meant. He kindly told me that if a succer player who belongs to a professinal team plays succer very well, that is so rude because they play succer for their living, it's natual to play succer well. Likewise,
If I tell a genius person "You are so smart". It's no surprising because he is actually genius.

That makes sense.