Just hours after havin' lunch with Michelle Obama ... and one day after stumping for the Pres at a Democratic rally ... Hollywood liberal Katy Perry sat down for a peaceful dinner with her ultra-conservative parents. 

Katy has some major philosophical differences with her folks -- who are very devout pentecostal Christians ... especially when it comes to social issues like gay marriage. 

But last night, they didn't let politics get in the way of a good meal ... and dined together at Red O in L.A. to celebrate Katy's 28th birthday. 

Wonder who paid for dinner?

From TMZ.com

Thumbnail via TMZ.com