I find that an engaging smile and a compliment to another's physique diffuses most situations. However the caveat to that is there will always be some asshole. I have the habit of casing any place I walk into (PTSD) and can spot the guy most likely to make trouble. He has a furrowed brow and a distinct RBF. He's the guy that if I have to come into proximity with I will go out of my way to be cordial with. Kindness isn't weakness. De-escalation is key. Short of that the same engaging smile and a jab to the solar plexus followed by a cross to the chin has been effective. Proper fighters don't go out of their way looking for altercations. The dog who barks the loudest has the weakest constitution. My .02

Its basically because the Bodybuilders look great and get a lot of attention, both off guys admiring their physique and wanting to look like them and women who find it attractive. Then you have the MMA guy who normally has an average or understated physique but knows how to fight as thats what he practices, so its more a case of wanting to show the bodybuilder up as the MMA fighter knows he will beat him in a fight. The bodybuilder normally thinks he is a much better fighter than he really is because he's stronger and bigger - but in reality unless he can get hold of the person and knows some submission moves he'll simply get winded and knocked out. However this naivety will probably get him involved with fighting the MMA guy. I'd never get involved in anything now that would risk my training, all too often I keep hearing of guys that lift tearing a bicep when punching someone in a fight! If that happens then its game over for that arm for a year.

In case you haven't noticed, your caps lock is on.

I'm a lover not a fighter.

Guys like that get smashed all the time. Just like Roid raging bodybuilders that think big muscles mean they can fight. They get smashed too. I’ve been a fighter since the 2nd grade. From cheesy Karate, to wrestling, to Tae Kwon Do, to BJJ, to straight up street fighting. I’ve beat the shit out of bodybuilders twice the size of me, and gotten my ass handed to me by a couple guys half my size. I fought a 6’ 5” fat dude once that wouldn’t go down. I hit him about 100 times with powerful shots, his fat ass just kept coming. Like Forest Gump said, you never know what you’re going to get. Most well trained fighters, won’t ever pick a fight. Too scared of ruining their lives and going to jail. Just like most well trained body builders don’t want to fight because they might win, but if they get hurt bad enough, they will not be able to train.

The real answer to your question is that there is always going to be that asshole. You will usually see or hear him coming. You have to know when to walk away before you become his target. Our pride keeps us there, almost hoping he will make the mistake of messing with us, but in my older age I’ve learned that if I’m not making a lot of money for doing it, I’m not interested. I’ll always defend myself without a doubt, but I won’t ever keep myself in a dangerous situation, regardless which of us is in danger. Get yourself out of the situation Asap.

I think that is def a person to person kind of bias.
The difference between body building and MMA is pretty apparent.
But the thing alot of people over look is the idea of SHOW vs GO muscles.
most MMA/Wrestlers/Boxers understand that Aesthetic DOES NOT mean functional.
Body builders spend a lifetime making their physique or "SHOW" muscle in-tune with their goals and ideals.
Most MMA guys start off as wrestlers, and as wrestlers in a calorie deficit the chance to work out the "show" muscles just isn't there.
Instead spending more time on the "go" muscles(the muscle groups used to move and throw another human being) which are two entirely different sets of muscles. They wont look nearly as greek god like but all of it is there for a specific purpose.

Granted if a wrestler/mma guys walks up to the bench press, im sure most body builders wouldn't give the guy the respect he deserves considering. Its all just a function of where your time is spent.

Speaking from personal experiences: We get a lot of dudes fresh on gear walking through our gym thinking that a 400 lb bench press will get them into the UFC, when unfortunately the two diciplines just DO NOT translate. My advice.. Pay your dues in the MMA gym the same way you have for lifting in the gym. Humble and open to learning.