Steve-O: I'm Down To Take On Isis ... With My UFC Buddy

We're about to reach a whole new level of Steve-O craziness ... 'cause he's freakin' calling out ISIS ... and he's doing it in the name of UFC fighter Tim Kennedy.

Kennedy's situation is no laughing matter ... the FBI was investigating "credible threats" against the fighter -- an uber Patriot -- earlier this year ... believing those threats were possibly coming from ISIS operatives.

Steve-O and Kennedy are buds ... so much so that Steve-O let Tim CHOKE HIM OUT at a recent comedy show ... and when we ran into the "Jackass" star at LAX he let it be known ... he's got Tim's back.

For the record ... Tim Kennedy is an ex-Green Beret ... Steve-O is not.

Check out the clip.