The main difference between this and a red herring or ad hominem is the preceeding claim/disproved process that is essentially ignored.
Named because this is often used by Republicans or Religious people, though it's applicable in any context.
B: Yes he is, and here's a copy of the birth record.
A: Obama is Hitler!
B: Nope, Hitler's dead, Obama's not, therefore Obama is not Hitler.
A: Obama's as bad as Hitler!
B: Obama has not directly caused the death of 11-17 million people, so no. (Wikipedia link)
A: Obamacare still sucks!
B: That was a bullshit republican argument that has nothing to do with what we just talked about, and I now think less of you for making that point, and less of me for allowing this conversation to go as long as it did before walking away. Good day.