This is what appears on my screen Pip.

"I'm dying to meet a BNP canvasser; I have a couple of terriers, one a feisty Jack Russell with finely developed political instincts..."

Not a threat - two statements of fact with a semi-colon in betweeen.

"the funniest sight in the world is a BNP canvasser in full flight down the street with three JRs biting at her heels...that'll learn'em to come knocking at my garden gate *LOL*

Again, this says nothing about what the commenter would like to happen in future. Hence not a threat.

And in any case, the Dangerous Dogs Act 1991 says nothing about threats.