It would be true if it wasn't for a very little, but important detail. It's NATO that threatens to attack Assad/Russia, not the other way around.
The whole thing is a farce. Assad should be the one demanding US coalition to feck off back to wherever they came from since they have neither official permission from the country's government nor UN mandate to conduct military operations in Syria. That's what international law says, no? Instead, the aggressor threatens the country's president and its ally with the use of force.