There is an idiom in my language, which literally sounds like "I'm not an expert when it comes to kinds of feces". Which means that one considers all the instances of some group as equally bad, not to make an opinion about any (for example, politicians). Is there an exact equivalent in English for it?

The original version is in Ukrainian. It is "В сортах гівна не розуміюся". In Russian it is "В сортах говна не разбираюсь". It's a relatively young, but very common expression.