This is a great point. I like to keep it as natural and organic as possible, I think we all need to decide where we put our boundaries.
If we use natural dyes and go on using toxic mordants, I think we are not doing much good to the environment. However, there are other ways of using natural dyes that are harmless for the maker, the environment and for the wearer.
Another critique towards plant dyes is that if the use of natural dyes increases, more land is needed to cultivate the plants needed for our dyebaths, this land could otherwise be used for growing food. What if we:
-explore local dye plants that are weeds and need to be cleared anyway
-use tree prunings
-grow flowers as a companion plant in between food plants
-use veggie scraps and fruit peelings
-use the dye plants more than once, so that less plants are needed, this will give different shades
-use waste from the florist
-use techniques that need less plant material to give colour
-when the plants come out of the dye bath, dry them and you can reuse them later, you can extract more colour that way
-by eco printing: using the plant material directly on top of the fabric, roll it and steam or boil. There is only very little plant material needed for this technique
-by using fermentation dyeing, especially the technique re-invented by Anne Rieger, using an acid and an alkaline bath. With this technique, a bit of plant material goes a long way and it keeps releasing more dyes over time.
Grow your own food, grow and collect your own dye plants!