Erik and Lyle Menendez are firing back at Los Angeles District Attorney Nathan Hochman … telling him it’s stupid to compare them to Sirhan Sirhan because they actually admitted to killing their parents.

The Menendez Brothers distance themselves from RFK‘s assassin in new legal docs where they push back on Hochman’s motion to withdraw his predecessor’s motion to resentence them.

Hochman’s on the record saying Erik and Lyle should not gain their freedom, comparing their case to the denial of parole for Sirhan … but the brothers say there’s no way to seriously put them on the same plane as Sirhan.

In the docs, obtained by TMZ, Menendez attorney Mark Geragos says the main difference between Erik and Lyle and Sirhan is the Menendez brothers fessed up to killing their parents, while Sirhan claimed his innocence in the Kennedy assassination.

Geragos also takes some shots at Hochman … claiming the new top prosecutor in Los Angeles is conveniently leaving out facts from the Sirhan case to draw a false comparison to Erik and Lyle.

The brothers admit they initially told cops they didn’t shoot their parents before coming clean at trial about the killings and then claiming they were victims of sexual abuse at the hands of their father … and Geragos says they’re now rehabilitated after 35 years behind bars and no longer pose a threat to society.