That's not in the least my main point, which you would know if you had been reading with your brights turned on. That's just one of a host of manifestations of sexual behavior giving a survival advantage other than by direct reproduction. Do you think it's a survival advantage for an outlier wolf to enter a dominence hierarchy, or do you think it's the most advantagous to be pummeled and killed or driven away.
It is, of course, not normal in good times like these, as for being natural--that's a slam dunk on the evidence: nature is pretty ruthless about adding doo-dads to creatures for no particularly good reason.
Your entire set of "arguments" (if they can be called such) are pretty much based on two premises:
1. The truth and validity of evolution, with extrapolation derived from animal behavior (defeated by Scripter above) and
2. Half truths and smoke-and-mirrors. Statements like "most marital abuse takes place in heterosexual couples". What a bogus statement. Why?
a) Only heterosexuals are marital couples.
b) Of course most spousal abuse takes place between a man and a woman since homosexuals are only around 2% of the population.
c) If you want to look at the abuse figures in truth, you have to figure it out using percentages of population, not raw numbers. Since homosexuals are around 2% of the population, what kind of statistics are there for partner abuse?