The noun double standard is countable. Looking at some ngram you can see the plural form used for titles (to mean something like the topic of...) or when there's a number preceding it (i.e. referring to a list: the 49 double standards...). But the results don't really show the plural in a sentence with a conjugated verb and a personal pronoun... For instance telling someone "you have so many double standards" doesn't feel completely right, or is it just me? I think I would use "different" here instead of double, and further explain what I mean by that (different standards for such and such thing/person, in this or that context etc. though I might end up using the singular form down the line: double standard this, double standard that).
Do you think a sentence like "you have so many double standards" is idiomatic (it has 2k hits on the search engines, don't know if that's a lot for something like this); is there a more natural way to phrase this (and if so how would you rephrase it)? If not, is this because there's something specific about this noun (is it just because it's not that much being used?) or is this more generally about the usage difference of the singular vs. plural form of the nouns/the way the verb to have is used (improperly/ambiguously?) with an object?