JC brings up something important here, and I'd like some insight from other ARMAteers on the issue, since he himself is busy:
If by refusing to condone sportifying of martial arts, an ARMA member refuses to bout with other HEMA practitioners under their rulesets, how can the two methods test each other? If the ARMA member insists on using the ruleset he is used to, the outsider can just claim the same indignation and refuse to play by ARMA rules. How are these two stylists supposed to test their mettle without drawn-out considerations of which ruleset is superior or more realistic first, OR actually trying to kill each other? How do you convince another HEMA student that their training methods are phony, while still expecting them to have a friendly bout with you?
This is a fair question, but the answer depends a bit on how you define rulesets. In ARMA we try to have as few rules as possible because the purpose of sparring is for learning, not competing. We don't keep score (except in Prize Playings, where it's necessary), we don't use judges, and we don't wear lots of armor or padding. Calling hits is on the honor system between the two fighters, and generally if you're getting beat, nobody needs to tell you that, but good sportsmanship is always required. Most of us protect head and hands of course, but otherwise safety is maintained by good control, and it should be evident from our videos that this does does not diminish the speed and energy of our free-play in any significant way. In my 15 years of doing this, I can count the number of serious injuries I have seen or even heard about in ARMA on one hand and have fingers left over, so I believe our method to be effective. We try not to restrict technique any more than necessary (if you're new, don't thrust until you learn how, and a few techniques that really can't be controlled in any way and still be useful). In these respects, I think most other groups out there should be able to get along with us and spar in a constructive and enjoyable manner. Regarding padding, we won't stop anybody from wearing as much as they feel necessary, but we will still expect you to not try and break us, and we'll do the same.
There are a few rules, particularly the "afterblow" and grappling rules, which would certainly require some discussion to come to agreement on. My personal view is that, as long as you can explain to me clearly the training value of what you do, then I am willing to try it your way for a few rounds if you are willing to try it my way for a few rounds. We have a few guidelines of our own for things like double kills, and we are happy to explain our reasoning behind them if asked.
The last thing, and the one we won't compromise on any more, is equipment. We spar with wood or steel. We tried the plastic wasters for a couple of years back when they first became popular and found them to inaccurate in behavior and inadequate for what we consider to be realistic training, so we will not use them any more. If that is a point of contention, then we'll just have to say so be it.
Ultimately, good sparring requires respect for your opponent, respect for the Art, and testing your skill as much as possible. If you can agree with us on that, then we can find a way to give each other a good fight.