I don't think people who abuse public figures on social media should get jail sentences. I don't think what they do is right or should be tolerated, but the sentences should be fines, community service, curfews and restrictions on access to technology.
I do think, however that a lot of crimes should attract a mandatory prison sentence. Burglars, repeat shoplifters, repeat offenders generally, people who commit unprovoked assaults in the street, people who commit criminal damage etc should receive a prison sentence regardless of mitigating circumstances.
I think that crimes which cause physical harm or financial loss should always be treated more seriously than a bit of abuse on Twitter, especially when the abuse is targeted at a public figure.
It's a bit like the guy who made a joke about blowing up an airport a few years ago, he was a bit of a dick but wasn't actually making a genuine threat. Goodness knows how much was spent going after him, money that could have been better spent imprisoning actual criminals.