I had to look up impermissible and the results essentially say it means taboo or socially unacceptable. Is this correct? If so then I feel experts claiming there is no such thing as an impermissible thought is probably to be interpreted as them saying all thoughts are acceptable even if they're of a taboo nature. Rather than thoughts of a taboo nature aren't possible which is how I first read and interpreted the statement.
I guess you're struggling with finding acceptance in society from what you say. I have no idea how far laft or right field your thoughrs or opinions are but if they're based in good logic then perhaps they're justified. Either way it's worth asking yourself that question and also asking yourself whether you truly care for acceptance. I have controversial views on a few hot topics so I think I know where you're coming from. It does make you feel segregated as a result but it shouldn't make you feel 'less than'. If you get my meaning. If your opinions are truly formed from fact and genuinely good logic then the issue isn't one that lays at home so much as it indicates an issue with the society you're in. I suspect I'm stating the obvious but it doesn't hurt to offer some reinforcement in this situation as it can really feel like you/we are the one in the wrong and can play havok with your self belief and confidence. People can be driven to madness from such circumstances and it might be argued its a form of passive gaslighting. Unintentional though it may be.
This only holds water if you truly are pragmatic and objective in your thoughts and views though. It's healthy and I'd say vital to always be asking yourself that question. Assuming you fit that description then fuck society. As a whole society is broken. Humans have been regressing for some time and it seems contagious. Europe is becoming American in its views on mental health and various other issues which creep into the public psyche like a wolf in sheeps clothing. People are happy to believe what suits them rather than what is, due to fragile ego, greed, narcissism and in some cases survival instinct. We're far from perfect and very few in society have a solid platform in which to judge others from. We all live in glass houses. Some of us are just more inclined to see it.