I figured your very hard-boiled description of the gang was a misdirection! I very rarely include totally irrelevant details in my puzzle statements...
Are any of the tattoos on the gang members relevant? no specific tattoo is relevant
are any of them also Sikhs? no
were they there to show everyone that violence against the Sikhs would not be tolerated? yes, that is an underlying message of the arrangement, but they weren't instructed to just stand around and look threatening
Was the old friend a member of the gang? the leader? assume this
did the commercant (I think I shall call him Mini-M...er Tad) know the old friend from before he entered the local CoC? yes
is either the old friend or Tad Sikhs? Indians? no to both