Line 3 does add up. How can something be an insult if no part of it is insulting?

'Wigger' is racist when use by a white man, since it includes the word 'nigger'. When used by a black man as an insult, it is racist, since the 'w' (white) carries negative connotations - otherwise why not just 'nigger'? When used by a black man as a compliment, it is probably still racist, since it carries the connotation that someone is not a bad chap, FOR A WHITEY.

Uncle Tom is NOT racist. An Uncle Tom is a compliant slave. The race of the enslaved and enslaving is incidental.