Tho Lionel mocked Archie, he liked Archie. He understood where Archie came from and saw who the real Archie was. That was something Mike Stivic was unable to see.
I agree that the characters liked and respected one another. Given Archie's prejudices, it was refreshing that he accepted this young, Black Man. I think it tended to "soften" Archie a bit. The two men had good chemistry on the screen.
From Wiki: A college student majoring in drama but with no acting experience, Evans caught his big break when All in the Family producer and director John Rich hired him to play Lionel Jefferson, the son of the Bunkers' new black neighbors. Show developer Norman Lear preferred Cleavon Little for the role, but Rich lobbied to cast an actor who would appear less threatening.
I agree with everything said here. Despite the notion some have of television doing a disservice to African-Americans then the only characters that stood out to me were Lionel Jefferson, Lamont Sanford, and James Evans Sr.. People of intelligence if not always allowed to use it and of heart.