Roleplaying with Xenos is a difficult subject. As a synthetic I don't want to speak Xeno because I believe it would be near impossible to decode their language and to speak it. I'd much rather just get a good look at them, and go back to assisting the marines. I really don't like becoming hostile with the Xenos as that is not my job, but there are some exigent circumstances that warrant it. If a marine has been pounced I'll push the Xeno off them, I'll throw random stuff at Xenos slashing cades or punch them at most. The only time a weapon will come out is if I was ordered to take it or major chance of friendly loss of life.
Oh also adding in some rules against synthetics in the Xeno roleplay guidelines would be too difficult to implement and properly enforce or would become very intrusive in what actions Xenos could take with synthetics. I've suggested making synthetics it appear like humans do where they can be seen through walls, or to make them slightly transparent in Xeno vision.