The Iowa Congressman was in D.C. Friday when he addressed the outcry ... telling us he's visited one of the centers, and found it totally hospitable. He raved about the kids getting exercise, meals, and a warm place to sleep -- not to mention medical treatment that surpasses what they get in their native countries.

Of course, what they they don't have are their parents.

King, a Republican, insinuates the Democrats are spinning this into a controversy, and adds ... the centers were open during Obama's administration and no one complained then.

One side note, relevant to the immigration issue ... King came under fire this week for retweeting British Neo-Nazi Mark Collett's take on immigration. He has not deleted it.