Dear
@John-Wick!
First of all, you are strong enough to beat someone rated 2400 :-)
Well, in your extreme example, when a 2400 rated player is masquerading as a 1500 and you are losing rating points to them, then everyone else will also be losing points to them on their way back up to 2400.
The effect is temporary: more points you lose to sandbaggers, more points you gain in your next games as your own ratings are getting lowered by them.
Please remember: Rating abusers and cheaters can take your points but they cant take your skills - you lose nothing, really nothing by losing to them. Please dont let them manipulate your emotions.
Just btw. it also works the other way around: sandbaggers give away free points on their way down...
I think dealing with sandbaggers in online chess is the hardest part.
You simply dont have the evidence unless people are making it absolutely obvious. :<
Just keep reporting them and help the administration of this site to keep the enviroment clean!
Happy chessing and all best. :-)