Boomer patient exploded because I wasn't overjoyed about his generous tip

I'm a dental technician. As such, I produce dental prostheses and repair them. I don't deal with patients very often because work is sent to the lab I work at via dentists. However, there are rare cases when patients come to the lab directly because they need a small fix.

Entry: this boomer patient who ranted about his prosthesis not fitting. He began to explain how he didn't wear it for months because "his wife complained about it smelling like shit" and how this wouldn't have happened with "reaaaaallll German quality work". (He looked around the room which contained a number of people who looked like they might come from foreign backgrounds, including me.) He then dumped this tartar- and food stain-infested piece of prosthesis onto my hand without letting me get gloves or at least a paper towel, dumped himself onto a seat next to my table and stared at me menacingly.

As you can figure out, he didn't ever consider cleaning the thing which lead to this hellish stench. Not wearing it for months also made his jaw atrophy which is the reason why it wouldn't fit anymore. (Yeah, these prostheses do more than just looking pretty, lol.)

So I started to work my way through the years of dirt that encased the poor thing. I used a bunch of aggressive chemicals, a sandblaster and rotary hoes to get rid of everything and found a somewhat presentable piece of work beneath all the grime.

After 3 hours, a bunch of "can't you do it faster?"- and "are you grimacing?"-laments from the patient and lots of processing, the prosthesis fit again. He finally smiled and said "Didn't think a China girl could do the job!" (Disclaimer: am neither from China nor of Chinese descent) He then proceeded to dig through his wallet because he "stole my time" so he "had to pay my efforts in a respective way". The thing is, we don't charge our patients because everything is handled via the dentists, however nobody says no to a tip, right?

So he went through his wallet full of 100- and 50€ bills and I started thinking to myself "wow, that guy is loaded". Until he pulled out a 50 cent coin. "Here you go, I'm so grateful for your hard work!" I blinked and looked at him confused. Dude, it would have been less awkward if he had just said thanks and left. Did he even know the wage floor was at 12,41€?

I didn't notice how seconds passed, said "umm, thanks" and took the coin. He started fuming. "Is there anything wrong? This was a lot of money back then! I would have been happy about pocket money of this amount! Dirty foreigners come here and expect red carpets and money rain when they come here!" I then put on a polite face, ignored his rant, thanked him for his generosity and wished him a good rest of the day. He continued to nag a little more and slammed the door behind his back. I put the coin into our community money box while we laughed about that man's entitlement.

Edit:

*English isn't my first language, so I'm sorry if some phrases sound weird.

*My former boss (this happened a while ago, I was dismissed among others because he lost customers) was quite the people pleaser as long as it meant positive reviews and business for him. He'd "pat me on the head" and tell me not to take that douchebaggery personal, then invite the next one of that kind with a smile on his face. (He was also racist AF behind our backs, but as long as he had cheap workforce it was fine for him.)

*My stupid brain didn't think of "tip jar" when I typed the last sentence. We aren't allowed to claim money from the patients directly for legal reasons, however we are allowed to take tips. (Loop holes, right?)