Milkweed for dinner?

I tentatively brought a green stalk towards my mouth.  Could the familiar milkweed actually be edible?

Recently, I posted about edible dandelion greens.  Yesterday, I ventured even further into the realm of wild edibles.  

My kind neighbor dropped off some milkweed shoots, which looked a bit like asparagus.  After snapping off the root ends and boiling them in water for about 30 minutes, I steeled myself for the first bite. Surprisingly, my tongue registered the flavor as green bean - like.

A few weeks ago, a different neighbor convinced me to try cowslips, a type of marsh marigold.  I boiled those forever and enjoyed their spinachy flavor.

Last week, I learned that the leaves of the invasive garlic mustard, flowering right now all over Ithaca, are also edible.  Alas, I haven't had a chance to try them, but I've read that they taste less bitter if picked before they flower.

Is it environmentally responsible to eat wild edibles?  One person I spoke with questioned eating milkweed because monarch butterflies lay their eggs on the plant.  Another said that cowslips are too pretty to eat.  Others advocate eating garlic mustard because it is invasive and crowds out native species. 

Funny how this question of environmental responsibility arises so naturally when we forage for food, and how unfortunately easy it is to forget when we cruise the supermarket aisle.