I feel that just because you are a Dominant that does not mean another Dominant won't find you attractive or desirable. I would take it as a compliment.

On the other hand, it may be a vain attempt to boost the ego of the male Dominant. If he can "break" the will of a female Domianant, then perhaps he would feel that he could tame anyone? Just a thought. I also know (from watching) that some male dominants feel threatened by female dominants, that their masculinity is threatened or something of the sort, especially if he is only interested in the female of the species. If the male is a chauvanist, it may spur him on further.

Just a thought. (This in no way reflects on any of the Domiannts here)