Not the OP but familiar with some of these arguments.
Free trade is held to be pareto optimal outcome - you and I get cheaper tshirts, people in bangladesh get higher incomes because of tshirt manufacturing, everyone is better off because of comparative advantage, etc.
However, if we distinguish between development or industrialization, then free trade provides strong disincentives wrt investing in capital intensive industries where one does not have a comparative advantage.
If I have capital to invest in Bangladesh, it does not make sense for me to try to create a high-end equipment factory; German manufacturers are way more efficient and effective, so it will be very hard for me to compete.
The competitive advantage of my region is cheap-labour, so all investment will be biased towards that. Unfortunately, this means that it's very hard to create high-value-added industries that can substantially raise average incomes.
If we look into the historical record, we find that the industrial revolution was a period of high tariffs and protectionism; the British empire had a great advantage in acquiring raw materials but IIRC, the French textile industry was more efficient at the time.
As a result, they were incentivized to export raw resources and import high value added materials. This is a loser's game. Instead, with the application of high tariffs British manufacturers were now able to compete and thus were incentivized to develop their own industry.
Again, IIRC, you can basically take every well-industrialized nation and look back to the period where they gained their industrial edge and you will find high tariffs and protectionist policies aimed at protecting and developing their own internal industries.
(This is a decent segue into talking about how pareto optimal outcomes, without taking the initial distribution of resources into account, aren't automatically moral or just http://www.interfluidity.com/v2/5537.html )
TLDR: free trade makes things cheaper, and spreads money around, but it does not automatically make poorer countries substantially richer.