Um... Sorry this won't be what you want to hear, but you were out of line consistently.
Those people, the staff, owe you nothing short of showing you to your appointment and being polite. Winter time, early appointments, hall ways whatever it be... You are owed nothing more than anyone else.
I work somewhere where there is a woman who has bipolar and boundary issues, she shows up everyday with no business for being there. I work at a church and I have no business turning this woman away nor would I ever do that, but she displays the same emotionally needy entitlement I'm hearing from you. It interferes with my mood being around it and it is a distraction from my work. However, I am never impolite unwelcoming or rude. I can tell you if she ever called me a MF or whatever, Id have a long discussion with my boss where I'd insist on finding a way to not interact with her. It sounds like they approached your therapist and it isn't to bully you. You're crossing lines with them, they have every right to secure their work environment and to have emotions of their own about how your behavior affects their office.
Nobody needs to read through a letter for you, invite you to use their computer or anything like that .The employee who assisted you deserves a big compliment for going beyond her job expectation to be helpful. You showing up there without an appt would bother me too. I would question your presense and probably feel annoyed... Sorry. They have expressed issue with it, so you should respect it and find somewhere else to go daily.
Your therapist sounds more than tolerant. You should step back from this situation, analyze where you have gone wrong and quit blaming people for being just as human as you. You got annoyed by their annoyance. You called them out of their name, they'd be fired if they did anything close to that...
They locked the door. Hello. They asked you in so many words to respect boundaries that you are trampling over. No one is perfect and I'm sharing my opinion to give you a more balanced perspective in hopes you aren't too prideful to adjust your views here. You didn't act your best. Your entitlement is off-putting in this situation