Emotion, especially strong emotions, will tend to distract and bias your thinking. This is "obvious from everyday experience" which is why you don't try to do any difficult thinking while in the grip of strong emotions, at least not if you're rational. But this does not make them "antithetical".

Harry Browne, in "How I Found Freedom in an Unfree World", suggested the purpose of developing a personal morality is to have rules to guide your actions when you are too emotionally engaged to think rationally. You think out the appropriate responses to various situations and problems rationally, then use these responses as rules to guide your behavior when you don't have time or are too distracted to think rationally.

Emotion and rational thought are antithetical.

Emotion can work against, or in conjunction with, rational cognitions, depending on the specific case at hand. For example, hypocrisy tends to anger people, and desire to avoid hypocrisy may lead people to avoid contradiction in their views (I say "may," because of course not everyone will even scrutinize themselves for hypocrisy, only others).

Reading about something like Lysenkoism makes me mad, but that emotion might actually inspire people to be more rational, rather than less, in considering science.

Emotions are but one of many heuristics in coming up with arguments (i.e. Reichenbach's context of discovery), which is fine as long as we have a rational justification for that argument (context of justification). If emotions are so strong that they are impinging on the context of justification, not just discovery, then I agree that there would be a problem.

If you take a person and remove their emotion, you don't get Spock off of Star-Trek, you get someone completely unable to make decisions in their life, someone who can think of no rational reason to chose one flavour of crisps over another and dithers for hours.

Inappropriate emotion can certainly cloud judgement, but removing the emotions all together won't help make you more rational I don't think.

I'm rather conflicted in my response to this... ADBOC, I suppose. (Agree denotatively but object connotatively.)

On the one hand, I agree with you that emotion distorts reasoning -- especially negative emotion. However, it's the desire to suppress negative emotions that powers most "motivated reasoning" -- i.e., we try to explain away our fears and setbacks.

But this means that pretending to not feel negative emotions, leads to precisely the distortion you seem to be saying you're concerned about.

In contrast, we have no reason to explain away positive emotions, nor do we generally feel the need to randomly make up explanations to feel good about -- if we feel good, we generally just feel it, and are maybe motivated to DO something about it. (We don't normally sit around reasoning about it, unless we also have some fear about being happy... in which case it's the fear that motivates the reasoning.)

So while your statement is literally true -- negative emotions motivate distorted reasoning, and positive emotions don't necessarily encourage ANY reasoning... that doesn't mean that suppressing or ignoring emotions is actually useful!

To engage and eliminate negatively-motivated reasoning, it's necessary to first face the facts behind the emotion in question. You can't be an emotional illiterate, and still be rational.