Can you picture the MSM uproar if a Trump supporter sent that message to a Hillary pledged elector? They would be calling for his head on a platter. The Feds would be investigating not just the sender but Trump as well.
Also, I think [but not sure] it is a federal crime to send terroristic threats through the mail or over the internet. Is there any investigation ongoing about these threats? Haven't heard of one.
Let's get real people. If even one elector changes his vote because of the threats, then this country is gone and won't gome back. the statement by allosaur would become common place and rule of the gun would replace the rule of law.