This is going to be blunt, but here goes: just because Floyd Mayweather Sr. fucked a woman and gave birth to Jr. does not automatically bestow upon him the title of "father." Genetically, yes, but it's a title you have to earn. After all, if a father gives birth to a son, and then is never there for his childhood, what kind of "father" really is he, having played no role in his "son's" life?
Being a father/mother comes with certain responsibilities. How good of a father was/is Sr. to Jr.? Only Jr. truly knows the answer to that question. We should not speculate how a person is based on edited television episodes and selective articles and glimpses we see. Let me be clear: I do not condone what Jr. did to Sr., but it's apparent Jr. does not see him as much of a father-figure, otherwise those words would have never been said. No "father" would EVER pray upon their son's downfall or wish bad upon them, and Sr. continually has. I don't care how bad of a son Jr. might be; you have a duty as a father/mother to show unconditional love to your child. There is a reason why Jr. gets along with his mother so well and not his father, and no matter what Jr.'s temperament is, I doubt such hateful words would EVER come out of his mouth towards his mother.
You are a product of your parent's upbringing (how much of that is nature vs. nurture is still hotly debated). The way you conduct yourself and the foundation for your morals and ethics usually directly reflects upon your parents, or whomever raised you. The fact that Jr. acts the way he does and can talk to his father in that manner most likely means he was not raised with the very foundation that seems normal to most of us. On top of (and maybe lending to) the fact that the Mayweathers lack any formal education, we constantly see the Mayweathers (namely Roger and Sr.) use words like "motherfucker" and "faggot" all the time, leisurely and at will. Therefore, the fact that all of a sudden Jr. can explode on his father with those very words should come as no surprise, now should it???
I know as a son/daughter you are supposed to respect your parents, but you have no choice who your parents are and how they act towards you. On the contrary, as a parent, you MADE THE CHOICE to have a child, so it is YOUR responsibility to raise your child/children right and treat them well, and if you have done so, that respect will usually be returned to you two-fold.
And just remember:
Before you criticize someone, walk a mile in his shoes. That way, if he gets angry, you're a mile away, and you have his shoes.