Why should we have to respect religions?

[Sasaki Kojiro]

So respect for opinions are not based on respect for the person holding them, but on the worth of the opinion itself? And there is also a hierarchy in the worth of opinion?

The words respect and opinion are a bit troublesome I think. Are we talking about respect in a "live and let live" sense, or in a "I admire this" sense? Are we talking about opinions as things that people believe, or purely subjective beliefs?

You can respect a person and think that their beliefs are false or ridiculous.

Should respect for a religion be based on the theoretical / theological worth of the religion then?
Do monotheistic religions deserve more respect than polytheistic ones? More than animismtic? Or are they all, however fundamentally different, of equal theoretical / theological worth?

A religion that supports doing unto others as you would have them do unto you is (arguably) more respectable than one that doesn't support it.

Does Scientology deserve as much respect as Lutheranism? Is it common courtesy to respect Scientology? If a weak-minded person, socially isolated, in adverse circumstances, is recruited by Scientology, do we respect this as a common courtesy, or do we faill him?

This is why "common courtesy" isn't really an answer.