Here is an indisputable fact. Unions raise the cost of goods and services and taxes. How are higher taxes and higher cost for goods and services good for the economy?
Perhaps you could offer just a shred of proof for that assertion. Higher taxes certainly often mean a better managed and provided for body politic. Before we had roads, schools, police, a system of justice, any concept of public health or social services there were practically no taxes at all. Of course anyone not one of the rulers was little better than a slave with almost no rights at all. Is that what you call good for the economy? What benefit does a serf derive from even the lowest cost goods she cannot afford, and what's wrong with continuing the investment in such stuff as effective communications and transportation networks, an educated, healthy and orderly workforce and a system of laws aimed at ensuring all have confidence in fair and honest treatment in the marketplace and elsewhere. Do you really imagine we could get that for nothing?
Taxes bought us that. And we united together to decide on, earn and enjoy those benefits, whether we call the coming together a country, city, corporation, union, or any other kind of club or gang, it's all much the same. It's a fool's thinking to imagine it can be stopped, or that the 'other guys' club is worse than yours.
But before you say a fact is indisputable, you must establish that it is indeed a fact and not just an ignorant prejudice. How many factory workers could afford to buy a family car before unions and how many after? In truly meaningful terms, raising workers' wages (which unions had a little to do with over the years) actually lowered costs for such goods by expanding markets and sales. But that's getting into technical economics where neither of us should go, even if some will want to argue definitions of 'cost' vs 'price' or 'affordable' or '20's dollars vs. today's.
It is indisputable that a union that won better pay in a new contract has altered the cost side of the ledger, although only with the agreement of managers, never by themselves. Anything beyond that tautologous oversimplification of reality you must give some evidence for, especially if if you're going to generalize.
And as always allow for the role and responsibility of the other signatory to every contract. The one whose task is to manage costs. Don't their inflated and unjustifiable bonuses and salaries show on the same side of the ledger as the wages of workers still turning out unsellable cars their masters ordered up? Who cost GM more, the bad decision-makers in the Ren-Cen or the windshield installers in Oshawa? How would beggaring the Oshawa workers have made the cars better or their managers less blind to their own market?
We could go back to serfs, and I'll guarantee some would be so stupid as to want to (it was part of the official German plan for the Slavs) but to turn your question back. How would a population of serfs be good for the economy?
By the way: Union members who make better money also pay more in taxes. Pushing things the other way makes the 1% have to pick up even more of the tab. Just imagine: MicroSoft Regiment of Foot, Duke Stronach of Magna's Fusiliers and the Canadian Tire Mounted Artillery going off to war in some distant land. Maybe some primitive place where where they measure wealth with gold. Makes you think how far we've come since the bad old days doesn't it?