A warm sentiment to be sure, but wonder if it also applies to the orcs marching across the Pelennor, whom you know are intending or enslaved to deal death. Do they also deserve pity and mercy? If not, then why do mosquitos?
In the quote above, Gandalf only advises that one should not strike without need. In the cases of both mosquitoes and orcs, it's not at all clear that xenocide is requisite to ensure the safety of humans or the many dwellers of Middle Earth.
