I believe so, yes.

Yes, you're threatening chargeback

Well, yes, it's a threat. But it's impossible, there's no way they can downgrade you :p.

Well, right now no one can downgrade me :/
But in general anyone can buy you a rank.

Donations? Nope, if you have god etc, "You are not allowed" to buy a rank below it .
I was curious too, I was threatened.

You can be downgraded...

Technically you can't, but it's obviously illegal lol
You can threat people meaning it's illegal, but it doesn't necessarily mean it is going to happen

Long story short, it's illegal

Yes, threats in general are illegal.