So the challenge to you is not to argue for why sex is a spectrum. The challenge is to give a reason to think any of the organisms at intermediate points on that spectrum are still alive. They could have all died in the Precambrian.
We have individuals with varying degrees of intersexedness. And the doctors can't reliably assign them as male or female based on examination. How is that not a spectrum?
Hey, I don't have a dog in this fight; I was just pointing why your contention that in biology "most things are a spectrum" doesn't actually support your case. If you want to make the case you should consider the approach I recommended to Poli and seanie. You say you have individuals with varying degrees of intersexedness, so look through your collection and pick out the individual (or the syndrome) you think is the most clearly intersexed, the one whose sex organs are the most ambiguous or closest to half and half. Post a link to a clinical description. Seanie will read the description , and then come back with either, "Yes, I was wrong. That's an actual hermaphrodite." or "No, that's a man because ..." or "No, that's a woman because...". Assuming his answer is one of the "because..."s, the rest of us can read his explanation and judge for ourselves whether it makes sense. Any way it goes down, at least we'll have moved past the endless Monty Python argument clinic.