For those who do not know: cortisol is the "stress hormone". It's probably one of the greatest killers of humankind, ever.

Your brain dumps it out when you're under stress. It does stimulate the adrenal system... but being in a constant state of being flooded with cortisol will drain the life out of you. Eventually, you'll have a nervous breakdown. There appears to be a strong link between being filled with cortisol for a prolonged period and PTSD; think of a soldier in a trench in WW1. Constant fear of death, constant alertness, non-stop stress for weeks or months on end; suddenly we have this "shell shock" appearing in men; at the time, they believed it was a result of the physical concussive forces of shells exploding around a man constantly. Over time however, they found out it wasn't a physical injury- it was a psychological condition. Eventually this would lead to the identification of PTSD as we know it today.

This is why vacations, smoke/lunch breaks, etc. are so important. It gives the body some time to relax, let some of that cortisol work its way out of your bloodstream, then get back to work.

Cortisol is generally a performance reducer. Looking at MMA fighters, most often the fighter who is relaxed, calm, even having fun in the fight is going to win. The fighter who is tense, nervous, and jittery- they'll probably lose, because they're thinking too much. Cortisol affects your muscles, your reflexes, and your fight-flight system.

That all being said, I'm not sure that simply hating a subspecies of humans will cause all of this. Unless it's an OBSESSIVE hatred, where it becomes unreasonable- where the hatred cannot be explained with any rationality. I hate niggers for uncountable reasons, and I can show you why they fucking suck (generally, there's a handful of good ones, but they are the exceptional among them). However, look at the hatred niggers feel towards Whites- it's irrational. Whites have done nothing to niggers except build the "first world" and tolerate their presence in it. Not only do we tolerate them, WE ACT AS THE NIGGER POPULATION'S SURROGATE DADDY as our tax dollars feed and house and attend to their medical needs. But they hate us.

What I'm trying to say, is there is a difference between rational hatred and irrational, obsessive hatred, and I don't believe it's "unhealthy" to have hatred in your heart unless you cross that line into irrationality.

It's a stretch. Looks a lot like quackery.