A Penn State fan ain't apologizing for a letter he sent to a football player that many found offensive … in fact, the guy is DOUBLING DOWN on it, saying, "Get the guys cleaned up."
In case you missed it … a man named Dave Petersen wrote a letter to Nittany Lions team captain Jonathan Sutherland — begging him to cut his "awful" hair.
"Watching the Idaho game on TV we couldn't help but notice your — well — awful hair," Petersen wrote …
"Don't you have parents or girlfriend who've told you those shoulder length dreadlocks look disgusting and are certainly not attractive."
Sutherland's teammate tweeted out a picture of the letter … writing, "Explain to me how this isn't racist."