Rampage Jackson Says Son Acted Like 'POS,' But Syko Stu Deserves Blame Too

2:21 PM PT -- Rampage Jackson followed up his Instagram post with another in which he shared the video of Syko Stu apologizing to Raja before he was invited to go into the ring to fight him for the show.

Rampage says he hopes the clarification about the invitation -- since some people think he just trespassed and hit Stu -- might stop some of the threats he and his family are receiving.

Quinton "Rampage" Jackson's blowing up at haters online who are sending his family threats ... admitting his son, Raja, acted like a total maniac -- but, Syko Stu needs to take some blame too.

The MMA legend popped off on Instagram Monday morning ... sharing a screengrab of a commenter calling for the streets to take out Raja Jackson after he brutally beat down Stu in the ring.

Rampage shared a long Instagram caption ... in which he told people they've all gone too far -- namely, throwing violent and racist threats at him and his family.

Jackson says, "Yes my son took things too far, and I’m pissed at him for being a POS and the way he handled it! But if psycho Stu wasn’t drunk and wouldn’t have hit my son over the head with a (real beer can) while he was live streaming on his own stream then Knox wouldn’t have felt like they had to make things right by letting Raja get his “get back” in the ring!"

Rampage says he wishes Raja went to the cops instead of beating up on Stu at the event ... but, now he needs to "face the consequences for going too far, he knows better!"

However, Rampage thinks people are struggling to see past the wrestling storyline to realize where the line between performance and real-life fight begins and ends.

Jackson adds that the narrative -- that his son beat up a veteran with PTSD for no reason after jumping into the ring where he had no business being -- is totally unfair ... even if his son messed up by continually beating the man once he was on the ground.

Rampage finishes off his message, "Let’s all learn a lesson, keep your damn hands to yourself. If you get paid to do fake fighting don’t disrespect people that do the s*** for real! Now i put myself in this s***! Dm me now!"

As we told you ... Syko Stu is out of the hospital after the brutal beating Raja put on him -- and cops are still investigating the incident between Jackson and Stu.

We spoke to WWE Legend Mark Henry ... who agreed with Rampage's take -- arguing that Raja went too far, but Stu should've known how a non-wrestler might react to the whole storyline.