few flaws in your argument
he never denies claiming cop technically, he denies that he actually came out and CLAIMED cop. he later does claim cop
There is no rule that says SKs can't come back witha guilty, even the wiki says it.
Serial Killers have also been seen with investigation immunity like Godfathers, or Tracker/Watcher immunity like Ninja.
"Have also been seen" means that it isn't guranteed
Why did you limit yourself to saying you can prove beyond a reasonable doubt you are not mafia, but left off SK and werewolf?
the last one is such a BS reason as it actually has no fucking logic behind it. Cop is supposed to investigate who THEY think is scum, this is yet another time you claim to be doing something just because you post (i.e. your "look I am scum hunting because I said somebody committed a town tell" BS that you used earlier in the game.
Let's end this right now
1. Are you Mafia
2. Are you SK
3. Are you werefolf
4. are you any other sort of role that does not share the town win condition
5. if 1-4 are yes, how can you prove it without a reasonable dobt?
the problem is you can't, so unfortunately you will be lynched today.