I feel the exact opposite. Nothing turns me off faster than someone straining for euphemisms to describe the "icky parts" of two grownups having sex. I suppose if the narration is terribly florid to begin with a random "THROBBING COCK" would throw me off, but no more than a "STEELY MANHOOD" in plainer prose.

Because I imagine the two characters - usually adult males, in slash - being as uncomfortable about describing their dicks as the author is and it makes me break down in chuckles every time.