First, one quick note about the binary: anything outside of the binary of two different sexes based on the type of gamete isn't even the type of thing that we're talking about in this thread anyway. Your garden-variety trans person still has one of the two types of gametes in the bimodal distribution.
Discrimination: I think you have to mean unjust or immoral discrimination, correct? Because a neutral discrimination - that there exist in reality two different sexes, based on the type of gamete - is not unjust or immoral, it just is. Thinking otherwise is a category mistake. Given that, there is nothing unjust or immoral in acknowledging the reality of two different sexes based on the type of gamete. That some might use the fact of two sexes to discriminate lies with them, not with the fact.
I'm not sure what significance "biological reductionism" has, given the above, other than as a faint pejorative.
It's a separate question as to what we do with the fact of two sexes based on the type of gamete. All I've been trying to do here is to justify that two sexes based on gametes *is* a fact of biology, and an absolutely foundational one at that.