In that post, you seem to be making the opposite case: That you should not reject X (animal testing) simply because your argument could be used to support repugnant proposal Y (unwilling human testing); you say that the indirect consequences of Y would be very bad (as they obviously would) but then you don't make the argument that one must then reject X, instead that you should support X but reject Y for unrelated reasons, and you are not required to disregard argument Q that supports both X and Y and thereby reject X (assuming X was in fact utility increasing).

Exactly. This is because the overall goal is increasing utility, and not a societal norm of non-discrimination. (This is of course assuming that we are consequentialists.) My arguments against discrimination/speciesism apply at the normative level, when we are trying to come up with a definition of utility.

For any given characteristic, different people will have different amounts of that characteristic, and for any two groups (male / female, black / white, young / old, whatever) there will be a statistical difference in that measurement (because this isn't physics and equality has probability epsilon, however small the difference) so if you tie any continuous measurement to your moral value of things, or any measurement that could ever not fully apply to anything human, you're racist and sexist.

I wouldn't classify this as sexism/racism. If there are sound reasons for considering the properties in question relevant, then treating beings of different species differently because of a correlation between species, and not because of the species difference itself, is in my view not a form of discrimination.

As I wrote:

It refers to a discriminatory attitude against a being where less ethical consideration i.e. caring less about a being's welfare or interests is given solely because of the "wrong" species membership. The "solely" here is crucial, and it's misunderstood often enough to warrant the redundant emphasis.