The logic you're applying here would have all accounts frozen at a bank when a single customer disputes a charge, all parcels held when a carrier misdelivers a single item, grocery stores unable to sell food when one customer should have been refunded.

No one is siding with Ryanair here. But laws can be enforced and justice can be carried out, without disrupting the lives of everyone else. There were likely on the order 200 people on that flight who would have been caught in the crossfire of a dispute they have no part in.