Premise: Recent moves to lower the tariff on Spring lamb imported into the United States have met with protests from sheep ranchers in the United States.

Conclusion: These ranchers complain that the United States' market would be flooded with cheap frozen Spring lamb imported from Argentina and New Zealand and that they would be forced out of business.

Now, let's examine each option to see which among them would be most damaging to the United States sheep ranchers' position.

Option A - Incorrect:
The subject matter here is on the stand of sheep ranchers in the United States on the recent moves to lower the tariff on import Spring lamb; it has nothing to do with the economists' point of view on tariffs. Therefore, this option cannot be considered.

Option B - Incorrect:
Well, the possibility that the United States' market would be flooded with imported cheap frozen Spring lamb is a concern to the United States' Sheep ranchers and not the taste differences in both the frozen Spring lamb and fresh Spring lamb.

Option C - Incorrect:
This claim focuses on the possible provision for an alternative lighter and less fatty meat, to Spring lamb due to the fall in sales of Spring lamb within the United States. This claim already deviated from the passage's main point. Thus, it is incorrect.

Option D - Incorrect:
Well, this claim appeared to have a significant impact on the United States' Sheep ranchers businesses rather than it will cause damage to them

Option E - Correct:
Well, the initial high tariff seems to have affected non-American sheep ranchers from importing Spring lamb into the country, and which thus gave the American sheep ranchers more edge to export to other countries where it's needed.

Also, it's perceived from the passage that sheep ranchers from Argentina and New Zealand offer cheap frozen spring lamb and if the United States importing tariff fee on Spring lamb is lowered to favor them, it will most likely lead to a crash in the price of sheep lamb in the country. As such, the American sheep ranchers may be forced to lowest their standard price to still be in competition, and thus will affect the price of the spring lamb they are exporting. Hence, it can force them out of business in the long run.