Is this adapter configuration safe?
You might get a tingle from EMI Y-caps but it shouldn't be unsafe to touch the ground pin assuming everything else is in order.

However, the unsafe part of this is that your ground pin is now not grounded, and the chassis of whatever equipment it is powering could become hot in the case of a fault.  That's the unsafe part about using the adapter in the manner you're showing.  If you do use it that way be sure to plug it in to an outlet with ground-fault protection.