> Pollution of any kind is just externalizing, out-sourcing the costs to others, its not fair.

That's way too simple, imho. Things come with side effects, usually. Of course, we should not pollute more than necessary, but the fact that there /is/ pollution is just a side effect of having

  - a civilisation
  - an economy
  - better overall health (and, thus, more humans)
  - ...

This all makes it possible to pay for welfare. In that sense, collecting taxes would be just externalizing the costs (of being dependent on welfare, thus being unproductive) to others.

The question, if we should do both is not a question of what sounds more fair, more justified or whatever. If it would turn out that "repairing" is more cost-efficient than "preventing", then why bother with the least effective measure?

> We can achieve zero emissions. Its really simple to tax-more-and-more-if-you-pollute in whatever form be it air or pesticides.

Some emissions are simply unavoidable. E.g. producing meat produces methane. So, taxing it would certainly bring down the demand for high-emission products (because of their now higher price) but as long as these products still exists, you won't go to zero.