If you read my post, I was in the open because I was ooc trying to get somewhere when you found me.
don't do this, this is the absolute fastest way to shitty roleplay situations nobody is happy with, xenian or not. if you're ooc, stay ooc; if you're ic, stay ic. if you're ooc and come across a situation you'd like to become involved in, don't just make the snap decision that oh, you're ic now - go find a way to introduce your character to the scene properly, rather than popping out of thin air, so to speak.
otherwise, what's already been said is on the money; headcrabs are ambush predators and the best way to create roleplay with them is to do things like hide in people's kitchen cupboards, fall out of air conditioning vents, fall asleep in their fridge, something like that - something where you're mutually startled, they don't already have a gun out and plenty of time to get ready for you to literally walk into their line of fire, etc.
pirate didn't powergame; as has been demonstrated, you had been yourself. i think the problem here is that you're expecting what most tnbers expect on their human characters - which is to win, and prove how great their character is. this is a bad enough mindset in that context, but when you're (subconsciously, i'm sure) doing it on the weakest, most vulnerable of xenian creatures which are intended to generate brief encounters rather than longterm character development, it turns into a disaster waiting to happen.
while i'm here i'll kill two birds with one stone and say this is a recurring problem with event characters, xenian or otherwise, and certain examples involving event overwatch going rogue or event rebels not doing what the event organiser needs them to do are further symptoms of tnb players' utter inability to separate themselves from not only their characters but
whatever character they are playing. stop it, all of you.
pirate's an abrasive fucker but that's just how it is, and in this situation he was entirely in the right. if you don't want people to get shitty with you, then you need to stop and wonder why they're starting to get angry rather than double down on your position; more often than not it's for a good reason, which can be talked out.