In any group of people there is always going to be politics, cliques, and factions. It's only human nature. It's true of BSAC clubs, PADI schools, GUE entities  and even groups of people who 'just go diving with no politics' (does anyone remember that YD trip to Scapa which fell apart in a huge argument and half the people went home after two days?).
Now I'm not saying that it's right or desirable, but it happens.
So - what would I do in your situation?
1) Work out where you want to be once this has finished. I'd suggest it would be an active dive schedule with a tolerable relationship with the Chair and Safety Officer, and unaffected at work
2) Work out how you're going to get there. You'll need to think about:
a) The 'judicial' process. Certainly my club has a constitution which sets out the details of how and why members are suspended. I think there's nothing wrong with suspending someone from diving if a serious allegation is made, but it needs to be serious, and then resolved quickly (which this one isn't) and the full accusation presented (which this hasn't).
b) The rights and wrongs of what you did. You can ask the internet for the answer (and I agree with what you did, based on what you said above). But as others have said that won't hold much credibility with your club. You need to get a regional or national-level person in to adjudicate, and perhaps officiate when your case is heard.
c) You need to think about how this affects your relationship with the SO and Chairman. If you want to crush them, then yes, I'm sure you could probably do that. However, the harder, but more benefical way of achieving your objectives (look back to (1) above) is to give them room to wiggle out and save a bit of face. I'd therefore be inclined to say something like: "Obviously I understand that you're responsible for diving safety in the club, and so adopt the most cautious approach possible, but here I think my actions have been mis-reported. I can see why you think using a pony on an ascent as normal diving practice might be an area for concern, but this was a training situation where I'd briefed my buddies beforehand, and you might not be aware of that..."
It might not be as satisfying in the short-term but (for me) it would be better in the long-run.
 - Not sure what the GUE equivalent is