Verbal Kint
Superstar
So Ned should've let him grow up in Flea Bottom like Robert's b*stards?

No, nikka. But real talk even being an apprentice to a smith like Gendry is a far better life than heading to the wall. The books are full of b*stards doing things. Sansa was supposedly Littlefinger's b*stard daughter and she was going to marry a nobleman. A b*stard was on the small council. Being a b*stard doesn't mean its the Wall or nothing. Ned is the one that let Jon make that choice without guiding him elsewhere. And Ned could've done any number of things to help Jon out or give him a future.