Not legal advice........I'm not sure what you mean by "its silent on the issue." If there isn't language allowing them to terminate the lease for a specific reason, then it doesn't exist, and they must perform for the length of the lease. I can't comment on every states laws, but I would be shocked if there was a law that unilaterally allowed tenants to terminate a lease for the reason you gave. (Please don't tell me this is the case somewhere out there.... Please!)
If it were me, I would work with them and try to find a "well qualified" replacement tenant. I would only let them out of their lease obligations until that new tenant was placed.
I'm not sure if this is an A-D property, but you also need to weigh the likelihood of your tenant intentionally causing damage as retaliation. Use your judgement.... If this is a lower end rental with that potential it may make more sense to let them walk then to go down that path.