But entering into such kind of disputes as which flag admins of club decided to have would be political discussion - something that has to be avoided here.
If other participants of WCL feel offended by some choice of 1 club from their public profile (description, flag, amblem etc.) they can simply ask organizers to review that internally and privately ask that club to revise that to prevent any further discussion. Because as much as any club has right to choose whatever as their symbol - to participate in a league they must respect other participants as well and not cause problems, IMO.
However, what was presented here is different to that - asking about players flags. not team flag (by the way now that I checked profile of Tabriz club, it is not Azerbaijan flag there, but the location - which also maybe is a problem for other Iranian clubs from WCL and team can be asked to update that info if necessary)
I can see some sense in both points of view.
I think that one relavant point to consider, in order to solve this dispute, may be that "Team Tabriz" itself flies the flag of the "Republic of Azerbaijan", not only a portion of its players.
The city of Tabriz, however, happens to be located within the borders of another state: the Republic of Iran.
I am reasonably sure that that flag (indeed very beautiful) is not meant to represent the Azerbaijani cultural identity, but only the state of Azerbaijan.
Now Tabriz, the modern city, is not a part of that state.
I think that this fact may risk to be perceived as a 'political' agenda (for ex. by Iranians).