Wayne Kirby, 49, was handed the sentence after leaving remarks on Mr Javid’s Facebook page last summer.
The Northolt man called for the Tory politician to be “hung, drawn and quartered” if anything happened to the infamous far-right activist. He also called Mr Javid “a Muslim terrorist”.
He ended his post by saying Mr Javid should “legally get ready to die boy”.
Kirby served six years after being convicted for rape in 2007, Westminster Magistrates’ Court heard.
The Tommy Robinson supporter was also found guilty of possession of cannabis, which breached his conditional discharge of a previous class B conviction.
Sentencing chief magistrate Emma Arbuthnot said: “The use of the word ‘boy’ was to humiliate the politician and there was clear racial and religious undertones.
“It was deliberate and hostile and this is something I take very seriously. Why should politicians and their staff work in this threatening environment? You say you didn’t mean it, it was out of character and it was idle but the trouble is that some people do put this into effect, as we have seen in the past.
“You are a loner and have no relationships and I accept it was sent on the spur of the moment.”
Kirby, who said he had been due to start a new job cleaning out wheelie bins, was fined £250 in relation to the possession of cannabis and also ordered to pay £150 in costs.
Detective Inspector Phil Grindell, from Scotland Yard’s parliamentary liaison team said: “As this investigation shows, we take all reports of crimes from MPs very seriously and we will deal robustly with incidents of harassment and abuse that are brought to our attention.
“It is not right that anyone is harassed, intimidated or obstructed because of their job, and we will fully investigate any reports of crimes against MPs or their staff and look to bring those responsible to justice.”
Additional reporting by SWNS