A cursory glance at discussions online regarding relatinoships and attraction would show that most people would say they don't decide who to be attracted to, that it simply is what it is.

Just because we can show that cheating has evolutionary benefits and thus people are likely prediposed to cheat in certain situations does not eliminate any moral considerations. Morality is precisely the idea of overriding any base instincts with what we "know" to be proper behavior. Claiming your genes made you do it is no more a loophole for morality now than "the devil made me do it" was before the discovery of DNA.

There was actually a study that showed female rats are more attracted to (read: had sex with) male rats with very different immune systems. The way she senses this is by the pheromone (smell) he gives off and as a consequence, her offspring have stronger immune systems.

In other words, this study suggests at least to some degree we don't even choose who we have sex with. Haha.

The purpose of my comment was to point out that humans have a (sophisticated) brain, something critical that you had overlooked, and you still seem to have missed that.

You argued that "who we have sex with is a choice we make by thinking about it, not something pre-encoded by our genes." I was trying to suggest maybe the opposite is true to some extent by sharing that study regarding the rats with you. Female rats unconsciously have sex with male rats whose pheromones smell like their immune systems are very different, in other words, who they select as mates is something pre-encoded in their genes.

Are you arguing that because we have brains we can 'override' what our genes would otherwise have us do?

there's a lot of stuff that people do that has nothing to do with thinking, and i'd argue that the idea of "intelligent choice" explains pretty much nothing in the context of mating/pairing. example: why are some people of the opposite sex "your type" and some not?