Don't wanna burst your bubble or anything, but if i'm on a packed tube train the person next to me dosent give me a 30 second warning to move before punching me in the face until i'm dead as that would be considered unprovoked. Given this is exactly what the Thargoid did yesterday when i was 900m away i'd say unprovoked attacks are pretty rife with the Aliens

.
Further more yesterday myself (and there are videos of several others) who have been hyperdicted and shot at before the ship even reboots by 3 Thargoids...sounds pretty unprovoked to me.
To use your analogy, if you stole the guy on the subways backpack, refused to give it back, and then he gave you 30 seconds warning before he started punching you, you'd probably consider him to actually be pretty laid bad and reasonable.
All the evidence points to
us invading the borders of
their space, we found "barnacles" and started mining them (by shooting them) and taking the resources for ourselves.
We then started finding Unknown probes and artefacts and started taking them for ourselves. We found ground bases and broke in, stealing more stuff, shooting the drones they have there doing whatever it is, stealing data, scanning everything, taking resources, etc.
We then encountered the Thargoids, and everything we've visually seen (not speculated upon) has been us shooting first. We even made special weapons as fast as we could so we can shoot them, we're even having competitions to see who can kill them fastest.
If you imagine these same situations happening in reverse, so say one of our Frontier mining outposts is being raided repeatedly by aliens who have suddenly started appearing all over the borders of our space, and actively tracking down our bases and breaking into them, stealing our probes, staling resources from us...
We'd go out gunning and shoot every single one of them we found, hell we did that even though there's little evidence of them being actively hostile. The fact that the Thargoids are pretty passive shows they are truly restrained. I've been all over the Pleiades since the Thargoid return and had dozens and dozens of encounters and never once been shot at except when I was carrying a UP or staying too close to them after being warned off. Even then I get the feeling it was more warning shots than trying to kill me.
The only questionable thing they do is take escape pods from the wrecks, but we have literally no idea what they're doing with them. They might be collecting them to return them to us, they might not even know they're humans, they might just see something "strange" and want to investigate it. We literally don't know at this stage.
If I were in charge of the governments I'd task the military with stopping people attacking Thargoids, issuing bounties on anyone that does, make it a criminal offence, at least until we know what's actually going on.