Part of the answer was public sentiment. A few currents of public opinion converged here:
- The European political left is traditionally anti-American, and much of the moderate populace is America-skeptical.
- The left, including the moderate left, is rather pro-regulation concerning product, workplace and environmental safety, workers' rights etc.
- Each tariff has a particular interest supporting it, akin to tax exceptions and subsidies. Like those, they are notoriously difficult to abolish, even if they are overall detrimental. On occasion, the particular interest coincides with a strategic or public interest (ensure European autonomy regarding some strategic items) which makes it even more difficult.
- Some of the free trade negotiations concerned food, which is an exceptionally delicate, so to speak, topic. Food is an expression of culture and as such is used to define oneself and distinguish oneself as a group.
All these social, cultural and and psychological currents could be examined in the case of the famous "Chlorhühnchen" (chlorine chicken).
In the U.S., chickens are routinely rinsed with a chlorine solution prior to packaging to reduce the bacteria load, increasing customer safety. This practice is forbidden in the E.U., and customers, including your author truly, had pretty strong opinions about it. Among health concerns, an argument that resembles objections against geo-engineering was made: Simply sterilizing bacteria-laden chickens masks bad production practices; the bacteria load should be minimized by producing at higher standards, not through after-the-fact remedies.
The "chlorine chicken" became a sort of meme for everything that is wrong with free trade, and TTIP in particular.
The following chart from a pro-free trade essay by the Adam Smith Institute ("using free markets to create a richer, freer, happier world") illustrates customer sentiment nicely. The question was:
"Do you trust European or American food saftey [sic] standards more?":
(Note: As the commenters found out, the chart accidentally swaps the two tall columns — Americans have less trust in their own regulators.)
The trust Germans have in U.S. food safety is immeasurably small. (If it is any consolation: They are also somewhat skeptical towards their own.) It is no stretch to assume that the opinion about regulation in other fields, like the mentioned labor and environment, was similar. Generally, the argument was that products that are only cheaper due to a disregard for workers, environment, product safety and quality should not be allowed to squeeze out the high-quality, high-standard European ones.