Your premise is, that to the Secret Service, there is no difference between an assassination threat and an assassination attempt.  

Here's a bet for you, let's say you THREATEN the President's life verbally in public, online or in a letter. Yes the SS will pay you a visit and question you, and go from there depending on your answers. 

But if you took a gun and ATTEMPTED to squeeze off a couple rounds at the President, what would the SS instantly do to you? (Hint- They wouldn't be asking ANY questions) 

Are you starting to get the picture, wanna take the bet?