Are we there yet?

On my way to the Cabin:
Father: Look! Its a Harem of females. Where's the buck holding them together?...
Me: The buck is... the baby?
Father: What?! No. Its the Big male deer.
Me: .... I thought Polygamy was illegal in Alberta.
Father: They're Mormon deer.
Mom: ...?...

I suppose this would be the basic comical happenstance to the unknowing person, but to those with their higher-thinking thought organs whirring in there skulls, they would hypothesize at a higher level.

When did global religion become a household (or in this case, highway-held) common theme for humorous suggestions in day-to-day conversation? When did it become okay to use peoples ethnic backgrounds in the basis of our nonchalant interactions?

I am not trying to shine a light, nor ameliorate, but am simply purposing a conundrum.

My answer? Somewhere between eighth and ninth grade.