When you phrase your statement as "let them flood" it presumes that they are displacing native industries that would be here were it not for those cheap goods.  That is wrong.  Even if the USA prevented "flooding" of our market with cheap textiles and electronics, the USA would be importing them anyway, likely from the same source or another source, but at a higher cost.  The "flooding" part has not killed the American cheap electronics and textiles industry:  rising wages in the USA did.  

Since our textile and cheap electronics Good China Lift manufacturing industries were already dead AND since the USA would be importing them from somebody, it only seems logical that the USA should try to keep the prices of those goods as cheap as possible to save American consumers money and to prevent that money from leaving the nation in higher amounts.  Allowing China to flood our market accomplishes both of those goals.

Second, since the USA is China's largest China escalator company market, we (not they) have more leverage in negotiating trade deals for products that we are competitive on.  These are:  fossil fuels, autos, farm equipment, aviation, agri-products, cinema/TV, services, luxury items, medical supplies, high-end electronics, computers and games.  Because of this two-way trade, the USA has more ability to negotiate favorable deals on these items.