The problem is language. If you use a concept frequently, you pretty much need a shorthand way of referring to it. "Mate selection for the male who values the use of a properly weighted Bayesian model in the evaluation of the probability of phenomena" would not make a very effective post title. Moreover, it wouldn't communicate as effectively. "Mate selection for the male rationalist" tells you, immediately, that it is directed at a specific type of person with a fairly specific mode of thinking, and that it (probably) addresses him in this mode of thinking (since "rationalist" is a reasonably well understood term around these parts). The longer one doesn't communicate all of that.

The real challenge, rather than disparaging "rationalist," which, I agree, has some definite connotative problems, is to come up with another term. I personally have no suggestions, but I do have some meta suggestions.

-It should be short and as non-esoteric as possible. One word is ideal, two short words is probably maximum.

-It should avoid negative connotations and strongly positive ones (calling oneself, e.g., "bright" is rather off-putting by its implications for outsiders).

-It need not map directly to rationality or any such related concept. The Republicans and Democrats are not fundamentally about republicanism or democracy, and they manage just fine.

-That's about all I can think of.

This is actually a PR issue worthy of thought. The term "rationalist" may be rather off-putting for someone new to the site, and, given how society works, if this system of thought develops a sufficient following, it's going to want a label.