Another way to say it is "if you're not of the society, you will be outcast and blockaded from any chance of winning."
Literally anyone can run in the Democratic primary, you just have to be registered as a Democrat, which is just filling out a form where there are no wrong answers.
Have you even been following the NYC primary at all? "Ideologically enforced" is hilarious. The difference between, say, the current #1 and #2 candidates Adams and Wiley is basically the difference between Trump and Bernie Sanders, and the the rest are everything in between and then some.
If you think anything is being ideologically enforced in this race, if you think anyone is being "outcast and blockaded" -- I mean, this dude Paperboy Love Prince [1] is actually on the ballot, not even joking -- then quite frankly you're delusional. This isn't Communist China, this is the Democratic Party which is, well, famously a bit of a mess.
I don't know where you live or what news you read, but if you're trying to claim America isn't democratic and open then, ha... you sure picked the wrong race to use as an example! :)
Fake democracy where you get to choose viable candidates exclusively from one party, and only one party.
Aka a party dictatorship, the same as they have in most authoritarian states, and ideologically enforced in a similarly regressive manner. If you're not of the party, you will be an outcast and blockaded from any chance at winning. The opposite of democracy, and very clearly so.