I've played with people like that. It isn't fun. No offense to the OP, but "that guy" ruins it for everyone else with the constant outbursts. Yes, you've paid your money to play golf and you can be entitled to your own particular idiom of how you play. But I paid for my round as well and I don't pay to be subjected to someones infantile rants over a bad shot. But I will give the "you're not that good to worry about it". I play with a "temperamental" guy who is prone to outbursts on occasion. One time I told him if he ever did something like that again, I was walking off and he would have a tough time getting me to join him again. I'd rather play solo. Well, he did- an outburst that involved LOUD cursing (language itself doesn't bother me) and trying to helicopter his club over the green we were on. Except he missed (story of his game, actually) and it flew barely a foot over my head and stuck into the green nearby. Fortunately, nobody was on it, but it took a divot. I walked over to the cart, grabbed my bag and started to walk back to the clubhouse. He looked at our other friend and started calling ME names for quitting. He just shrugged and told him I was right, and that HE was the problem today. Some more grumbling and cursing (I got this later from the other guy) as they moved to the next tee. I was further up the hole on my way back to the clubhouse, when I heard the cart kind of rolling up behind me. He seemed to have gotten the message and started the apology train, but I stood my ground and said that chances are we might not ever play again. I had told him before, if he did something like that I was outta there, but he didn't believe I would ever do it. Well, he doesn't go out and play by himself, he doesn't feel he's good enough and would be embarrassed. And if we don't play with him, he wouldn't play. That kind of sent the right message. Then he was a bit more sincere in the apology and I sort of let him off the hook. I asked him if he fixed the green he damaged. He said no.. Well, THAT sent me on a bit of a twist, and I let him have it for not fixing it. If someone from the course had been around, he would have been ejected and he better get back ASAP and fix it as best he can. If he cant fix it, he will tell the guy in the pro-shop what happened so they can take care of it. As he headed back, I called my friend and told him I'd wait at the 10th tee until they got there and we would take it one hole at a time, but don't let him know that. When he saw me waiting he was pretty relieved and embarrassed at the same time. Since then, he's had his little episodes but he is no where near the toddler he used to be. He KNOWS he's not good enough to be that angry, and even if he WAS that good, it isn't the right thing to do.
"Those guys" affect my game and the others because you never know when an outburst will happen. If he hits a topper or chunks one and starts on his ranting and murmuring, it may not stop while I'm setting up my shot. He might turn away and not be paying attention to what I'm doing and blurt out something right as I'm ready to play. I've had a few "Tiger" stops at the top of the backswing when they'll get that one last "MOTHAF**KER!" out of their mouths. I will stand and wait til he turns around to ask if he's done yet so we can move on.
As you say in the original post, you looked at your scorecard and said you were "on pace" to break 90. What made you look? Did you feel like you were playing well? Then that's all you should need. As mentioned in many of those "why do I blow up when I'm playing good" threads, it is the kiss of death. "Oh, I only need so and so to break whatever". And proceed to mini golf it around for the next few holes. If you feel you're playing well, then you probably are and don't total up till you're done. Make it a surprise. You can tell how you're doing usually after 6 or 7 holes. Go out with 6 straight doubles or worse and 90 probably isn't in the cards anyway, so don't worry about it. If you go out with 3-4 pars and a couple of bogeys, leave it alone. Keep that feeling going.