The same argument advocates monopoly or central planning by government?
If not, you have to jistify where is centralised enough. Now, if we have a 20,000 different bakeries, is that actually centralised?
Decentralisation of plumbers doesnt mean everyone does his own plumbing, it means anyone willing to learn can become a plumber and there is no plumbing monopoly.
Also we should debate the actual subject, not debate it indirectly throufh analogie, it just introduces an extra step of inaccuracy and cultural baggage.