It depends upon how you look at it. Yes, if you are looking at global gross production, protectionism takes that number down. If you take a manufacturing company say and shift the production to China, Chinese production goes up, excess profits which theoretically are reinvested elsewhere go up and prices go down. It seems like a win for all involved, but it isn't in all ways.
If you shift one company or industry to China or take your pick of developing economy, it is not a major problem as the developed world (Europe and US) can adjust. If you wholesale shift virtually all manufacturing to China, a good deal of IT to India and other countries, call centers to Manilla, etc, etc. You eventually have a situation where all of the services, or at least a good majority of the services/products are being created in one section of the world and the consumption is being driven by another section of the world, US and Europe. It is unsustainable as US and Europe cannot continue producing way, way less than they consume. Right now the US and Europe, to an even greater extent, are in hock up to their necks. The systems needs to rebalance where the developed nations are producing more to pay for their consumption. Even at the low prices from the developing world, we can't pay for the consumption. The Chinese in particular, but other countries as well, are sterilizing their currency to avoid inflation. This will have to come to a head at some point because the Chinese cannot continue buying US bonds forever to keep their currency undervalued vis a vis the dollar, which basically means the Euro as well as it is the dollar is the currency of exchange.
Food for thought.... If you are one of those that believes in national autonomy, the global shift of wealth from the West to the East is basically a veto on anything the Chinese and Russians do not like coming out of the US and their friends in Western Europe. The US and friends supposedly "won" the cold war, but it is interesting to note that the Communist countries that lost the cold war have control over our economies. If the Russians and Chinese decided that they were just going to dump their trillions in US, UK, and the rest of the EUs bonds, they would lose a bunch of cash and hurt their economies as well, but they would destroy the West's economies. The interesting part is that they don't need to actually dump the bonds. It is enough that the US and the Europeans know that they had better not mess with their landlord. The threat becomes the reality. It is ironic that the Communists may have won the Cold War round 2 using capitalism. What if in 1980 something the comrades got together and said, "The current approach to beating the West is not working. What if we superficially opened our markets to the West, allowed Western corporations to use our labor forces through state sponsored entities to transfer all of their wealth to us while making it profitable for the corporations as well. After we have effectively purchased enough Western government debt to control policy making, we wouldn't need to send in the Migs as we would have pretty close to full title over the governments and economies of the West." If you haven't noticed, the Chinese and Russia are still basically state run countries through artificial companies closely linked to state power. They may not be as committed to capitalism, and are certainly not as committed to Western style liberal democracy, as some might like to believe. Regardless of how you look at it, the governments of Western nations are far less powerful within their own countries and within the world than they were a generation ago.