If they start lobbing nukes, there will likely be plenty of volunteers from the areas hit.
In dogmush's scenario of setting a tactical nuke off in Crimea (presumably in response to a Ukrainian offensive into the area) it is a little more complex. Maybe Ukraine has a bunch of Crimean natives in their air force, but I doubt Russia would nuke cities they claim as their own, so even if someone born in Crimea were upset about the nuke, I'm guessing it wouldn't be targeted at civilians.
While it is absolutely an escalation risk and a reduction in the barrier to more general use of nuclear weapons, I'm not convinced a tactical nuke would be a particularly effective tool to use. Sure, if it were deployed against an urban area it would kill a lot of people, but it's not like Ukraine is going to be fielding mass formations of unprotected infantry in Crimea where a tactical nuke would be devastating.
If Russia did use it operationally (as opposed to a demonstration which would probably be merely treated as a treaty violation and used to justify sending more money and equipment to Ukraine) it would likely not be very tactically effective and it would strategically be a nightmare for Russia.