Here's the thing; The only thing we can prove for sure is that Thargoids are attacking ships that are holding items of Thargoid origin and refuse to drop them, and ships that they perceive to be hostile. If an innocent but trigger-happy adventurer gets interdicted and opens fire first thing they do, then that's on them for eventually becoming a floating piece of scrap in an NHSS. A human overreacting the same way to another human would meet the same end. That's self defense. If someone's collecting Thargoid sensors for personal gain, clearly without having asked the Thargoid for permission to use their thingy for whatever, then again, that's on them for meddling with objects they know nothing about, and have no right to claim for themselves.
We know that plenty of pilots, both players and NPCs, have been plucking Thargoid objects out of their natural habitat and trading them back and forth for a long time now. What if a Thargoid sensor or probe has a similar function to, for instance, a human nav beacon? What if an alien just pops out of nowhere and starts picking up our nav beacons and running away with them? We players wouldn't care much, but presumably the normal citizens of the Elite galaxy, those without discovery scanners, rely on these things for basic navigation between worlds. That'd wreak havoc on our infrastructure! And let's imagine that they're not trivial to produce, that each beacon maybe holds important information that can't be easily replaced (or perhaps information we can't let potential enemies gain access to), then it'd become a top priority to get them back. So we find them, floating in strange, unknown shells in space, and we tell the shell to let go of our thingy, and some of them do so we pick them up and fly back home, but some of them don't, so we shoot them open so we can collect our thingy. I mean sensor- I mean nav beacon.
By the way, you know who else has been blowing up humans ships to collect Thargoid sensors?
Pretty much every player who was involved with this whole mystery before we found the "UA shell" around Merope. And then, again, with the "UP" situation. We are, ourselves, far from above destroying an innocent convoy to get at these things, and they're not even intrinsically important to us outside of being fun and mysterious objects we don't understand! Who knows what meaning they carry to the Thargoids? If they need them back by any means necessary for a greater cause, then perhaps all these human casualties are objectively a drop in the galactic ocean compared to what consequences might come, otherwise.
Those military convoys, by the way, the ones that we first encountered the Thargoid sensors and probes in and then proceeded to assault in the name of science? They were being escorted by Federal ships. And which ships have we been finding countless wrecks of, damaged by Thargoid weapons, before this "return" became public knowledge and more factions became involved? Federal ships. It's not farfetched at all to assume they were only destroyed as a consequence of stealing Thargoid technology from under their... mandibles. So maybe the Thargoids did in fact open fire first. It's a perfectly reasonable assumption. But it may have had reasons, and even if some Thargoids have been shooting humans, not all of them do.
Think of it like this: If they are intelligent or patient or reasonable enough to deal with us on a case by case basis, never judging a commander by his comrades' actions, even if just sometimes holding their fire despite having lost allies or family to humans like us... then why should we not do the same?
