Many (not all) Vulcans come across as somewhat condescending. At least, to me.
I don't believe that attitude is entirely logical. Even if you believe logic is superior to emotions, condescension is a partly emotive response, which I wouldn't expect from someone that has his emotions
fully under control.
Also, a logical person would understand that such condescension is not conducive to convincing other species (such as humans) that embracing logic is the superior approach. It will, in fact, create more of a barrier for others to do so.
But of course, condescending Vulcans make for more interesting stories and scripts