Why are people dumping before the Oct. 25 fork 

Because nobody gives a flying fuck about Bitcoin Gold.
Actually, some of us actually could give two fucks. But that's about it.

I know futures are what they are, but the thing is probably less shitty than we expect...
https://bleutrade.com/exchange/BTG/BTC -> 0.05 BTC
That is worth a few fucks if it keeps the price