You might have an argument if racism, sexism, and homophobia suddenly disappeared. But they haven't. And even if you want to claim there is racism against straight, white, Christians, and/or men, it hits those people very differently.
Hence the debate over the definition of "racism": there are biases (which we all have, regardless) vs. the effect of bias.
So if I woke up tomorrow and every Black person in America hated me, it frankly wouldn't have much impact on my life. They would be biased against me, but I wouldn't feel much in the way of racism.
That is, your argument has a hole in it as long as mistreatment does not fall equally on all parties.
Another hole is that for the American rights, discrimination based on gender/gender preference/genitalia is central to the philosophy. LGBT bashing has been the #2 go-to move after abortion as long as I've been alive. Without those two unifying forces, the GOP would shatter. So if you're going to take a shot at "the left," you have to accept that some of this stuff is the literal fault of the right.
Then one more is one I suspect you will reject out of hand, which is that even if discrimination equalized tomorrow, the effects of systemic discrimination will linger for generations. So it's not enough to just announce we need to move past it. I'll suggest the following for you to check out.
