Friend at school confessed to me - is this weird or not?

[Im not telling!]

He told me that when he was little, he would ask his dad to tie him up in his underwear and TICKLE him!!! And the thing is his father actually did it...like, alot when he was a kid. He was about 5 or 6 years old. Sometimes he would be completely nude! I didn't know what to say when my friend told me this. Wouldn't this scar him mentally for life or something? Am I the only one who finds this strange?
No, Kevin, I'm not making this up.