No, it's not defensible.
Biblically, withholding sex from one's partner long-term is prohibited save for a few special reasons having to do with health. The wife is wrong for doing so.
But, her wrong does not give the husband the right to also do wrong.
The lawful Biblical resolution to the problem would be the annulment of the marriage, and the forfeiture of the dowry. The husband would send the wife back to live with her parents, assuming they were still alive. If they were not, she would effectively be homeless.
Obviously, things have changed a bit since then, but that is how the Law of Moses reads.
Jarrod