Stephen Baldwin Photog Incident NOT Alec's Fault

6/23/2012 7:38 AM PDT

Stephen Baldwin had big bro Alec Baldwin's back last night ... telling TMZ that his brother is not to blame for laying that alleged smackdown on a photographer earlier this week.

The Baldwin brother (Stephen, that is) was outside Katsuya restaurant in L.A. Friday night ... where he gave us some insights into Alec's confrontation with a NY Daily News photog ... and he's adamant Alec has changed his ways.

Stephen says his brother wouldn't get violent without good reason. He adds ... if a pap instigated a "situation" ... any reaction is pure human nature.