If Matthew Shepard had been a gay activist and was found later to be a meth user as well, then you might have a logical point.
But Matthew Shepard was a nothing but a meth dealer. He was not an activist, not an innocent victim, and certainly not a victim of the straight community. His killer was a bisexual man who spent lots of time in gay bars. Shepard was a victim of his own community and his own drug dealing.
Incidentally, MLK was not perfect and there have been many attacks on him, some justified (he cheated on his wife).
I saw somebody post somewhere a thing about how Rosa Parks was involved in a civil rights group prior to the bus incident that led to her arrest, as if that somehow taints her story of being too tired after working all day to give up her bus seat to some crackers.
Nothing new about any of this. Rosa Parks was a local leader of the NAACP in Alabama. Her taking the seat at the front of the bus was a calculated act; the NAACP had been looking for a way to make a stand on the bus issue.
The American public may not have known that Parks was an activist, but the rest of the situation was genuine: Parks WAS black, she lived in a state that DID discriminate on public buses (and everywhere else), and she DID take a real risk in taking a seat where she did. All that was real.
Matthew Shepard's story, on the other hand, is a compete fake from beginning to end. He was not killed for being gay, but as a result of the drug trade he was in. He was not killed by a paranoid straight homophobe but by a drug-addicted bisexual partner looking for a fix. The anti-gay defense of the killer could have been dissolved completely if his bisexuality, frequenting of gay bars, and his sexual background with Shepard had been brought to light.
There was NOTHING genuine about the Matthew Shepard case. There is no way to even compare a cheap, small-time meth dealer who had sex with his male customers to Rosa Parks or MLK.