Weird, does he say what the item was anywhere? I wonder if there are some things that are technically allowed but trigger fraud flags when newly created accounts buy them with certain payment providers. Either way, terrible customer service...
In any sort of 'case' like this, it's very important to have all the facts, and refrain from jumping to conclusions.
People are very quick to jump on the outrage bandwagon.
People who are challenging the ToS themselves are generally up front about what they are trying to trade, arguing that it ought to be allowed.
That said, this corporate approach of 'you are permabanned and we are not going to explain why because security' is just bullshit, essentially corporate dictatorship. Would you accept living in a country where you could be arrested, but all legal details would be withheld to prevent future crime? Of course not (I hope...though some would). The fact that this behavior has become standardized among tech companies is a major negative strike for the securocrat mindset and the prioritization of profit over anything resembling ethics. If you work for a company that has a policy like this, or uphold such policies, you are part of the problem.
Definitely, if I had been suspended and my only transaction was buying, say, a calculator. I'd probably be asking "Why are calculators disallowed?"
If I was buying plutonium, I'd leave that detail omitted.