Board Game Arena

I was really shocked by the outcome of this game.
My opponent went into negative time and I ignored it.
I was very distracted while playing, with kids and wife around,
but I held my own and I think I could have even won the game.
So I considered what my opponent did to be very unsportsmanlike.
It seemed desperate and rude.

https://boardgamearena.com/6/chess?table=227144032

These aren't real chess clocks so I'm wondering how expulsion is even allowed.
I mean I let him go into negative time and ignore it, was I wrong?
That game took a lot of points from me, for the loss (-13) and the expulsion (-10).
Am I wrong to consider this rude and unfair?

Certainly not sportmanslike, but his right to kick you just as it was yours to kick him when running out of time.

I should clarify that we were both dipping more into our time little by little,
and after he went into the negative I didn't think it mattered or would matter.
I think it was unsportsmanlike because it was a really cheap win, practically stolen points.

They need real chess clocks not the bs on this site. If you are out of time you are out of time. I played with a muppet recently who ran his clock down to -15 seconds then moved (wtf is minus time?) then when he was up next move he gets a minute thirty on his clock which he runs down to minus again and repeat. Not just chess but all games could have a fairer time system.