How cruel is all I can say.
Leave them be and they will not harm anymore.
A wasp does some good in our world, not like our real enemies slugs and snails.
Slugs and snails do help with decomposition of old vegetation. It is a shame that we have the mentality of slaughter anything that causes even a minor inconvenience, but I guess that is the issue with modern life, we have become ignorant and detached from the natural world, and see the natural world as something to be controlled or eliminated.
One reason slugs and snails cause problems is to do with selective breeding. Plants in the wild have evolved defense mechanisms such as bitter tasting compounds to deter animals and insects from eating them. The crops we eat are heavily human-modified versions of those wild plants. To make crops taste better, we breed the bitterness out, then complain when every slug, snail, aphid and pigeon wants to tuck into the sweet gourmet cuisine.