So jay mom ran his pops away for being a dike and having him rapping about daddy where you been...but she gets props and daddy is a fucc nicca in his mind
Parents separating (no matter the reason) doesn't excuse one parent or the other from being a mother/father.
That's what (at least in Jay's mind) made his daddy a "fucc nicca" as you put it.
"Why shouldn't I be mad?
Monster's parents separated, Monster had his dad
These parents had they problems, he still came to the pad
He bough 'em new bikes, imagine what that felt like"
None of that has anything to do with his mother being a lesbian or that being the reason they split.