My new rule is, if you can't call a person up to say something, don't text it. If it's inappropriate to call and say out loud, then it's inappropriate to text. The important thing to remember is keeping the relationship intact, or making a level-headed decision to set a boundary, or end it if necessary. You must treat the other person with respect, and you must love yourself enough not to push them away.
Reacting from anger is a trigger that causes your system to go into fight or flight, and anything you say will only put up walls and trigger the other person to react from their own story. It's not like the recipient will say, "Oh hey, I suck! You're right."
You have to communicate for a Win-Win. It's not functional to text in anger. Functional relating requires you to hold the other person at the same high-level in which you hold yourself, even when you don't agree or they hurt you. Anything less is toxic. You can't control anyone but yourself.
You can be mad, but those are your feelings. You can't control anyone with angry texts. You can't fix it. You can only deal with your own emotions and make decisions based on clear-thinking, not fight-or-flight.
So if I've ever texted any of you in anger (friends), I'm growing out of that habit. Now that I realize it's not effective, I think it will be easier to put the phone down, journal or call a supportive friend. Reactivity really is about YOU, not the other person. 
