Well im a bit disgusted by this.
Last year I was looking for a good deal for Far Cry 4 and Assassin Creed Unity as they were not on steam and would be my first Uplay exclusive games.
All I did was search for the cheapest deals and found Kinguin. Following that I made a few searches of 'is kinguin legit' and found nothing stating it was stolen or illegitimate keys. I just bought what I thought was a good deal and had no godamn idea of the shady market these sellers operate in and now I will potentially lose £90 because Ubisoft felt it would be better to punish me than act against the reseller.
Further cemented the idea that I will never buy a game exclusive for Uplay again. What a total shit, anti-consumer system. I say I have potentially lost the games because I'm playing Uplay in offline mode and now too scared to connect it again.
You blame Ubisoft for revoking stolen goods? You should blame the fraudsters for tricking you into giving your money to them instead of to Ubisoft.
Ubisoft is only protecting their business interests, if you were a paying customer with them you'd be included in that portion but if you decide to purchase goods from 3rd parties you always run the risk that something goes wrong, be it a revoked key or otherwise.
Ubisoft is far from the only organization that does this key revoking on a daily basis, every merchant that runs a legitimate business is victim of online fraud daily. Amazon, EA, Ubisoft, Valve, GMG, Humble Bundle etc. you name it, every single one of them does this, daily.
Then there's flip side to this situation, if you were to report a non-working key that you bought from G2A to G2A for example, they would probably jump on the spot to replace your key and make you a happy customer because to them they live on the ignorance of their customer base, plus replacing a stolen key with another is a very small cost (~$2-3) all things considered in order to keep up the charade.