I find your reply interesting on multiple levels.
For instance using words like "battle" that indicate I'm somehow in a state of pushing/forcing/challenging myself to do something incredibly hard and or unappealing.
There's also this assumption in many cases it seems, that it involves "battling" cravings, having to make careful plans to even have lunch with friends. This in order not to be swept away by this uncontrolable force that would make strong men weep. I have actually had friends fret over "helping" me by going down a list of restaurants, and for each choice, saying things like "Oh, no you CAN'T eat this, or you CAN'T eat that. No one seems to notice I don't ever say things like I "can't" (fill in the blank), or indicate in anyway I'm missing out on anything. It's not at all that I "can't" have xyz, I don't Want xyz. I don't perceive certain items as food anymore, no more than I would think that a doorknob is something to eat.
If I was in a long time habit of drinking gin and tonic, and then stopped that and drank plain water instead, no one would say "She's battling with the fact she can't drink tonic water"
I don't have any health issues in regards to my blood glucose. It's absolutley normal, and will remain that way into the foreseeable future.
I did have a problem with that at one point in time, but it's been resolved because I no longer eat the things that made that happen. I didn't have fluctuating blood glucose, never did. I had higher than healthy blood glucose, including dawn effect, which all rolled into one spelled pre-diabetes.
My pancreas was overworked, and at least some of the beta cells that produce insulin had died off.
Now my pancreas has a leisurely life and is not overworked. Part of that is hopefully allowing it to produce new beta cells.
If I went back to eating carbs, including bread, most fruits, root vegetables, I'm sure not only would my blood glucose levels rise, but the mood/emotional improvements and contentment would abate also.
Grains are inflammatory. Inflammation causes many physical and emotional negatives.
I'm not inflamed anymore.
So why would I want to go back?
Getting back to the original question though, I don't think, in isolation, eating meat prevents or causes a gentler temperment. I think it must be considered with other factors such as your complete diet, exercise, mental status, etc.
I eat a lot of fat. It probably has a lot to do with my overall satisfaction. As long as I don't add the carbs, it's fine, as far as my health. By eating a LOT of fat, but very little carbs, all my blood work has either stayed the same or improved, weight has drifted off 2 or 3 pounds a month, among other benefits.
An example I thought of far as fat is that it's like plastic explosives. Harmless in an of itself, unless it's attached to a blasting cap. That blasting cap is grain. We evolved to eat as much fat as we could, but we did not evolve to eat copies amounts of grain. The fact that 1/2 of us now have prediabetes currently enhances my belief.
If a person stopped eating meat and instead subsisted on a diet of microwave popcorn, 'Lil Debbie snak cakes and gin, I don't think anyone would be surprised if their temperments grew less gentle.
So, your question in isolation cannot be answered.