I just replaced my brakes all the way around and my right rear backing plate is a little bent and is rubbing on the drum slightly, and I do mean slightly should i tear it back down and try to fix or just let it grind off

 

I dont know how much grinding would be needed, but if it is just that slightly, try prying it out a little, and if no luck, then go ahead, as long as you dont leave any gaping holes in the back.. Dont want to fill the hub up with mud when out in the yuck!

 

When I said grind it off I meant let itself grind off/ wear in because it is a very slight rub

 

As long as its not so much that it gets red hot and throws tons of sparks for a long duration, LOL!