Re: surely trying to kill someone in a business quarrel isn't terrorism?
When the police are alerted to a bomb threat, do you really think that they assume it's not a terrorist ? What reason would they have to do that ?
While I understand where you are coming from, I think you've fallen into an assumption trap that's very the key point of the issue.
That a Bomb in a letter = terrorism
Could as easily be an attempt at a targeted assassination.
While a phone call, even to threaten or claim to have placed a bomb or random member of the public finding one in a bag at a public place could clearly be an attempt to sow terror, rigging one to specifically or attempt to specifically exact retribution by death or maiming is another.
I'm not saying either is at all justified, but blurring the distinction or assumptions due to current popular fears is not helpful.