justin why????

 Justin Bieber just got sued in Montreal by a promotional company that says he destroyed its biz with one little tweet. 

The promoter, Team Productions, says they had a deal for Justin to do an appearance at Beach Club last August. justin was supposed to do a couple songs and then hang out with fans -- but the event was scrapped.

Team Productions says it paid Bieber $250k when he signed the deal, and promised another $175k right before the event. But TP says it noticed Justin wasn't pumping up the gig on his social media ... as the contract required him to do.