It's iffy territory.
On one hand, the bar-owner (assuming he OWNS the bar) has the right to allow or dis-allow anyone from his place of business.
However, 'the bar' is a public space. Public places are watched over by the cities/states.
For the city to _order_ and _threaten_ the bar-owner to ban certain colors is barely in their place... (and only because 'the bar' is
considered a public sphere)
Then again, if the bar-owner called on city & state police for help, then he (I guess?) kinda left the door open for them to demand further actions be
Society demands that justice be had... but wants someone else to fix the problem. So the state/city steps in and attempts to legislate behavior.
To pick on all bikers because of one group of bad seeds is ignorant -- and yet the mentality runs rampant, and is socially accepted (at least insofar
as 'the people' giving the city their knee-jerk-reaction consent for this to happen).