Official response posted in http://mwomercs.com/...ploitsgriefing/
"However, we will not be tolerating players who repeatedly abuse this mechanic to grief their team-mates by killing them. Please refrain from retaliating against somebody who may have accidentally shot you due to a bug or confusion."
It could be interpreted two ways:
1. Firing upon someone who is on your side by trying to destroy you is akin to their behaviour, and will be viewed as such. IE, just sit there and take it.
2. The second sentence gives us a little leeway, because it says don't do it if they are firing upon you because of a bug or confusion. It stands to reason that anything other than an accidental shot would still be provocation, and repeated provocation is not necessarily covered within the text.
The problem in situations like this is twofold:
1. There is no clear-cut IN-GAME response to griefing.
2. The proof of burden lies with the accuser with little to no tools at our disposal, only the assurance from above that something is being done. No proof has been given in any case that anything has even been done, just the word that it has.
Here would be my suggestion:
If you are fired upon by a friendly, and can successfully identify who it is, do these things:
1. Try to block LOS between you.
2. Open peaceful communications stating you are a friendly target. Request to stop.
3. Distance yourself as much as possible from the aggressor.
If no response is given within a short time (maybe 15 seconds or less, depending on the firepower of the aggressor) declare your intention to retaliate. Don't use cuss words or negative language. Something like "If you do not stop, I and my teammates will be forced to fire on you."
4. Disable the enemy mech IF possible
a) If the mech has all weapons in it's arms like a splatcat, blow them off.

5. If no good option to disable the mech presents itself, destroy it.
6. Inform in alltalk the event as soon as possible, advise all parties.
7. Take screenshots.
8. Here is a grey area: I suggest all 14 others players to report the offender. This of course generates 14 tickets for support which may bog them down. HOWEVER, in order for you NOT to get reprimanded yourself, this is the best way to cover your own actions. Until an in-game option is added, this is what I would consider a necessarily evil. Sucks for support, but that's what happens.
Any other suggestions welcome. I'd love for some clarification from above. I understand this is not exactly the PGI recommended procedure, but truthfully there isn't much of a documented plan except for: "Let 'em shoot ya, sucks to be you."