Someone puts stuff into compost that won't break down and is toxic.

Then you use it for soil and eat it

So what ecosystem is that crowd avoiding?

Vegetables at a store or farmer's market, seemingly.

Perhaps your interpretation is right, but that would mean there's some group of people who simultaneously says "I know people put toxic chemicals into this industrial compost I use but I'm totally fine with that" and also "I only eat vegetables I grow myself". I highly doubt any such person exists.

I wouldnt know.

The take is that the microorganisms in compost somehow digest the dangerous chemicals and make them harmless...