My problem with it is the underlying ecological damage. There is a declining ecological space for these whales (due to krill fishing). OP was arguing that the argument for culling would be to keep them at this constantly declining number.
To use your deer analogy, it would be like cutting down half a forest ("fishing" the deer food), then saying you need to cull half the deer herd to keep them from overpopulation. Then judging by history, the forest would be cut in half the following year. Before long you have no deer left.
> There is a declining ecological space for these whales (due to krill fishing).
Is there any culture using krill for human food?
As far as I'm concerned, fishing should be completely banned in international waters -- this would also help developing nations that currently greatly suffer from commercial fishing emptying the seas close to their exclusivity zones.
To use your deer analogy, it would be like cutting down half a forest ("fishing" the deer food), then saying you need to cull half the deer herd to keep them from overpopulation. Then judging by history, the forest would be cut in half the following year. Before long you have no deer left.