I don't think that the average Leftist does "interpretation" at all. Not even a bit. They hardly indulge in political thought; despite the importance of what they call "theory" to them. That theory, even though theory, is itself rarely thought about - certainly not by your average undergraduate Leftist student. Even when the theory is stated, it's still not independently thought about. For example, at first you get:
"Blacks can't be racist."
Then you may get, on fewer occasions, this:
"Blacks can't be racist; they can only be prejudiced. Only people with political power can be racist and blacks don't have political power."
So even if that theory is true, which is certainly isn't, it is still often only stated by Leftists; it's not thought about or analysed in any shape or form.
That's why Leftists rely almost exclusively on insults and sounbites (cliches) - especially on FaceBook and on websites. This is funny because Leftists always talk about Tory or New-Labour "sounbites". It's as if Leftists, because they have Theory and Principle, can't, by definition, indulge in sounbites. But only Leftists believe this. Only Leftists would believe this.
These sounbites, such as "blacks can't be racist", and insults such as "racist" or "fascist", are used to stop their own thought; not only to stop debate. If you can encapsulate a political enemy in a single word (e.g., "racist"), or come out with a Leftist soundbite ("counter-jihadism is racism"), then you don't need to think at all. Most of all, you need not debate with someone who disagrees with you. He is too evil or "dangerous".
Virtually every Leftist has a tacit - sometimes explicit - commitment to a massive and universal No Platform Policy for all people who they disagree with. They pretend that it's because the person they disagree with is so evil or "dangerous" that their No Platform Policy is legitimate. But you soon realise that far too many people fall under that policy. Thus it is quite arbitrary and totalitarian.
In the 1980s these people had a No Platform Policy on the right-wing of the Conservative Party. Some applied it to the entire Tory Party. And because most Leftists belive that the Labour Party and the Conservative Party are indistuishable; then there's no problem with applying the NPP to New Labour too.
This No Platform Policy is no more or less that the contemporary version of the Gulag. It's nowhere near as bad as the Gulag; but that's because these Leftists don't have the requisite political power to make their NPP as bad as the Gulag.