Before posting my argument, I'd like to acknowledge the fact that I am not in favour of genocide as 'Pro' - the terms of this debate are unconventional. Strictly speaking, I would be the Con for this debate, arguing that African-Americans are not the subjects of ongoing genocide.
First, more clear definitions. Genocide is a specific term that was first coined by a Polish Jew called Raphael Lemkin who was a lawyer who migrated to the States because of the war and his writing was instrumental in constructing The Convention on the Prevention and Punishment of the Crime of Genocide (which is the UN's current genocide document).^1 The word genocide was first published in 1944, so it is a fairly new descriptor.
The destruction, in whole or in part, of one group of people must have specific intent and must be with the intention of completely removing that group (or that part of it) - you used the word "extinction". Typically, when we think of genocide, we think of mass rape in Yugoslavia, we think of Bosnia, and quintessentially, we think of the Second World War in which six million Jews perished in the bowels of death factories whose only constructed purpose was the mass execution of people to bring about their total obliteration. That was the only purpose.
We then counterpose this with the situation in the United States.
African-American populations residing within the U.S. have been increasing by around 4 million people per decade for the last 70 years^. Before that the rate continued to increase as well.
By definition, then, since the population is rising, there is no genocide taking place.
What we should be arguing for is social justice, equality under the law, fair treatment by the courts and law enforcement. There is still a long way to go before anybody can seriously be ready to say that social equality has reached an acceptable point. But when the Commander in Chief of the Armed Forces and the leader of the country is African-American, when the population is rising, and when there is no mechanised extermination process, a charge of genocide is both inaccurate and offensive to genuine victim groups of genocide.
Genocide is a term we reserve for the most egregious of mass atrocities. Injustice, even when it results in the abhorrent deaths of countless black men and women, is not synonymous with genocide.
Finally, on your irrelevant point about homosexual African-Americans, given that it's a free country, surely we should be advocating for our brothers and sisters to be able to participate in whatever way their conscience guides them? And since the African-American population is rising at an ever-increasing rate, and African-Americans identifying as any form of LGBTIQA is 4.6%^2, it's really not a demographic problem that needs worrying about. As long as they aren't hurting anyone, which they’re not, who cares?
Summarily, for the first round, it has been thoroughly demonstrated that the case of African-American injustice is not a case of genocide.