Take top control and apply as much pressure as you can 
To me, choke is the right answer
Tell the guy why its a bad idea to spazz out when he does it. If you tell him more than a few times and he persists, show him why its a bad idea.
Ingo Weigold -shark tank - after hurting a few guys because i kept applying more pressure on joint locks, i've figured out it way easier and safer to just choke these guys until they get rid of their ego. you can fight an armbar but you cannot fight a choke.
OK so you think forget about joint locks, just go for the chokes
I do this as well and my reasoning is this:
In a street or self defense situation, a joint lock may not necessarily stop your attacker.. I see it sort of analogous to the issue many carriers have with 9mm rounds. A choke however, will stop anybody. Big or small.
Mounted triangle and slap the shit out of him while yelling about budo imo
This is also, i think, where having a good pin and top control helps, If I'm feeling too much spazzy energy, I will get a hard pin and pressure them till they chill out a little. Chokes are awesome and one thing I've learned(after several spazz related injuries) is I can dial down my offense quite a bit to be nice but defense has to always be on point in case some newb tries to rip a foot off or overcrank a joint lock.
Shoulder pressure from top side control
"the spazz" is insecure. Instead of being insecure yourself and trying to intimidate them through force, apply empathy. Ask them to relax because it isn't about competition but about getting better. Competition is for tournaments or when two people agree beforehand to compete hard.
Let them know humbling themselves is the first challenge everyone faces in order to achieve proper open-minded self-development, so by doing it they're actually showing emotional strength in their ability to change by not fighting the process. Doesn't mean they need to take abuse, but it does mean recognizing that you're going to (and should) lose a lot before you get better.