Doesn't seem like the owner's grasp of English was super great. Might have just been a language issue.
Bad choice of words. I can understand their frustration though, lots of people park in that shopping center and go to the mosque on Fridays because of inadequate parking. Probably annoys the hell out of the business owners even if its only once a week for like ~45min. Should have worded it differently though and it wouldn't be a problem.
I agree that this sounds like a language issue. This could probably be resolved by letting he business owners know that the signs while for a valid reason conveys the wrong message. Also the mosque members could take it upon themselves to find other parking and also patronizing those businesses to build up better relationships with their neighbors.