'Reacher' Alan Ritchson's Neighbor Beaten Up After Calling Out Actor As a Menace

The guy "Reacher" star Alan Ritchson beat up on video is explaining how the fight started in the first place ... telling us he thought Alan was driving in an unsafe manner.

Ronnie Taylor -- the guy on video getting his butt kicked by Alan -- joined us on "TMZ Live" Monday and he told us Alan was driving his motorcycle way too fast through a residential neighborhood ... so he decided to leave his driveway and confront Alan.

Ronnie insists he had no clue Alan was a famous Hollywood actor and says he basically just told the guy to slow down so someone doesn't get hurt ... taking a stand the second time Alan allegedly came roaring down the block.

Of course, Ronnie was the one who ended up getting hurt here ... he's on video getting pummeled, and you can still see his battle scars from an epic beatdown.

Ronnie says he's an avid rider himself, and he was in his driveway washing his own bike when Alan came by ... and he jumped at the opportunity to give Alan a piece of his mind.