I don't find this anti-Spock argument very convincing. If the stove is hot, you just shouldn't touch it, there's really no reason to be afraid. Emotions were useful because they elicited the appropriate behaviour in the hunter-gatherer environment, but now we can simply manage, barring extreme situations, to do the proper things.

You can clearly point at rational behaviours and distinguish them from irrational ones, and you can call 'rational' an emotion which induces the rational behaviour. But that doesn't mean that the emotions, per se, are necessary to that effect.

A spock can really functions as a proper and winning rationalist... but we, of course, are no vulcanians.