You do not know what you're talking about, I am afraid.
LGBTQ persons are not protected by the Civil Rights Act of 1964 and can still be lawfully discriminated against on the basis of their sexuality.
Lack of protection under the law is not
institutionalized action.
What do I mean by that? It's the difference between "you will not be punished by the law if you refuse to give up your seat for John" and "John will be punished by the law
if he tries to sit anywhere."
There's a very valid argument to be made that private businesses should be allowed to discriminate, since the government shouldn't be interfering in voluntary interactions, and discrimination carries huge social and economic costs for the businesses that try it (in fact, businesses even today go out of their way to employ minorities and illegal immigrants BECAUSE people the government doesn't like for invalid reasons tend to be the most cost-effective labor).
There is no valid argument that government should FORCE or INITIATE discrimination. Thus, Jim Crow is no comparison to lack of protection laws for discrimination against people based on sexual orientation. So your first attempted argument reveals your ignorance of a key difference in policy and economics.
Before that, homosexuality was illegal and criminally punished as recently as the 1980s. Before that, it was grounds for institutionalization. Before that, it was grounds for lynching.
Yes, there have been buggery laws in various places. Alan Turing was prosecuted and eventually committed suicide in England due to them. But that was not an official, nationally-recognized policy that was carried out and enforced by formal institutions in half of the USA, as slavery was.
On top of that, sexual preferences are not visually distinguishable unless the person in question chooses to demonstrate it. Race IS. What's the difference? A homosexual person can literally walk right out of any town with buggery-laws and they have no way of knowing the person's status in regards to those laws. Black people could be and were detained, and apprehended and sent to slavers ON SIGHT in slave states if they didn't have free papers, and even that was for a limited time and assumed the papers weren't simply destroyed by the investigator.
If I didn't make you see this clearly enough, ask yourself why there was an Underground Railroad which required the coordination of thousands of people to free small numbers of slaves, and nothing of that sort ever had to be organized for gay people?
So no, buggery laws are no comparison whatsoever for slavery.
Your assertion that oppression of LGBTQ persons begins and ends at marriage equality is absurdly ignorant.
By this time this is over, every argument you make will have been destroyed and you will be making excuses to get out of this discussion.