Yes, it's naive to believe we can force 100% of active stake to vote honestly irrespective of the economic rules adopted
We can however, reward honest voting a lot more and dishonest voting a lot less, which is what the EIP is designed to do. Hopefully a very large portion, maybe even an overwhelming majority of active stake will want to participate in honest voting instead.
As you can see from the 'How do you Expect These Measures To Work Together to Encourage Honest Voting?' section, it'll require 2 good actors for each bad actor under the new system to close the pay gap between honest and dishonest voting. It's definitely worth a shot and we can tweak the numbers later.