I probably don't understand your point (sorry english is not my first or second language).

At this moment we're seriously overfishing our oceans and killing it's population, that's what i have beef with (pun intended).

So your argument is - let's continue fishing?

> any more than the vast land-use impact of agriculture can be used as argument for abandoning agriculture

I'm arguing for changing agriculture (or better land management practices), not its abandonment.