They do not accord to Allaah the Greatness that is befitting Him when they associate with him other than Him.
So when you bring Allaah to your jokes, you don't know who Allaah is.
"If you ask them (about this), they declare:" We were only talking idly and joking' Say was it Allaah and His Ayat and His Messenger that you were mocking?" Qur'an 9:65
"And they make the angels who themselves are slaves of the Most Gracious (Allaah) females. Did they witness their creation? Their testimony will be recorded, and they will be questioned." Q43:19
"Did they witness their creation? Their testimony will be recorded, and they will be questioned." Qur'an 43:19