I (21f) am 5'5" and skinny. I recently attended a self-defense class, and there I was tought how to use a pocket knife. And as I have some male friends 6'5"+ tall, I thought that that height actually makes their belly particularly vulnerable in case of a fight (compared to a short guy/girl):
- a short person's shoulder height is around the same level as the the tall person's belly making it easier to stab/hit;
- a tall guy's belly is proportionally a larger target.
And in general, if a 6'5"+ guy stands in front of me with his stomach released (even if he has just a bit of a belly) it feels like having an exposed, large and squishy punching/stabbing bag right in front of me, into which, if needed, I can easily harshly and deeply plunge anything straight away.
I also practice historical fencing (rapier) and most of the times I stab tall opponents into the belly - my favorite thrusts are ducking counterattacks when I duck while they attack, go low and impale a tall guy's unprotected belly right onto my rapier.
There's a time to run, scream and shout. There's also a time to fight like a cornered animal. It's all very situational. There's an entire spectrum of scenarios out there, and a basic self defense class isn't going to teach it. They'll usually give you a few "tricks" and send you on your way. I've been training fighting and self defense for 26 years, been teaching for 13. I'm just a random on the internet, but there are a lot of cons out there in this field. Many will claim to give you a silver bullet that will fix everything. There are no silver bullets. Some situations you're just fucked by default. Learning how to use credible, effective force within the confines of what society will accept and not send you to prison for life for is very complicated and takes a lot of practice. Even then, you might fail. Happens all the time.