TMZ broke the story ... a mom named Stacey Betts slapped Bieber with a $9.23 million lawsuit ... claiming her hearing was severely damaged at a 2010 concert when the Biebs "enticed the crowd" into a screaming frenzy.

Now Justin's firing back, claiming Betts' lawsuit is missing a few things -- like facts. 

According to the documents, there's no way JB could have known "pointing to a crowd" would cause a so-called "sound blast" -- and Betts' suit also fails to allege Bieber has any duty to stop fans from making noise.

Bieber wants the case dismissed ... due to lack of facts.

This is just ridiculous. So I can sue a donut shop after their donuts make me fat for making me unhealthy??? 

I'm on Justin's side on this one!