Unfortnately it would be damn near impossible to truly stop voting bots without affecting honest curation trails as well (which promote quality content, just look at steemstem distilled posts)

To make things worse you cannot stop a whale from self voting, however what could be done is something such as the Grumpycat initiative (I do not have a link to his post) and or build community flagging trails that work where people give their posting key to a bot owner which will then use the shared VP of everyone to flag posts that are not considered quality, however this requires communities to get together and join forces. If say 50,000 accounts (mostly minnows, a few dolphins, maybe a whale or two) were in it then it could be very powerful but then it might be too much power for one person (or a group of people) to control and yeah...

Basically if you want to fight this kind of abuse, use your voting power. Your response will be "But I do not have the voting power to take on [enter voting bot here]" to which I say I know... but there are others out there that are also on board and if everyone whom shared your sentiment worked together to fight the voting bots/whales then things might change. One thing you can do is if you have friends that joined steemit and decide to leave, have them give their posting key (private) to curation trails like steemstem or something as then they can work to fight against this abuse without having to ever do any work (fighting against by promoting quality content)

I use steemstem in this reply due to personal bias in knowing how it works, they could do it with other groups too, the point is that if they want to leave steemit due to this problem then by giving their posting key to a curation group they are promoting quality content and yeah.