Who's going to attack them - the pro-Russian gunmen occupying these places?
First af all, there are large areas with substantial presence of ethnic Russians, in the East of Ukraine, which are still under the control of the Ukrainian army. Second, Russians live
all over Ukraine, not just in couple of towns currently held by Russian insurgents.
So, to answer your question - who is going to attack them? Maybe you should ask this guy, an editor of Ukrainian TV station, accused for not being "patriotic" enough.
youtube.com/watch?v=8ihlldKy7jU
By the way, these thugs are members of the Parliament of Ukraine, protected by parliamentary immunity from persecution.
Also, in prospect of "anti separatist" military operation of Ukrainian forces, no one can tell right now, actually who will be in control of the Russian-held cities in the East in coming days, let a lone months.
These are all factors, which, may incline pro-Russians to refrain from giving an answer.
At the moment the only people being rounded up and/or executed in eastern Ukraine are people speaking in favour of a united Ukraine.
No one is being "rounded up and executed" in Ukraine so far, East or West. There where some skirmishes between militants and the army, and that is it.
But you're immediately excluding 67% of the population, how does that get you an accurate survey result?
As I explained earlier, you can not just presuppose that all those who had refused to answer, would, if willing, have given an answer according to your personal liking. Both pro-Russians, and pro-Ukrainians, in large parts of the country, have very good reason to keep their mouth shut...