It's part of the fun, at least!"Pox" is indecent? If she were writing an essay about the history of deadly epidemics, would she spell it "smallp-x"?
Is that some sort of Britishism?
Tit, by contrast, I sort of get, but the only fun part of Scrabble is the off chance of spelling vulgar words.

As to the use of these words, I feel a bit ambiguous about it. I always feel it's taking the easy way out, but rationally I can't find any reason to prohibit them. And I have succumbed to the temptation of za -- but what else can one do when presented the opportunity of scoring over 50 points with one tile?