The vast majority of us like to consider ourselves decent people. We pay our taxes, hold doors open for others, stay out of trouble, that kind of thing. I certainly thought of myself this way, a 26-year-old man trying to forge a career and get on with life. So when I was arrested on 13 January at work by four police officers, it came as a bit of a shock.

The reason for the arrest was a tweet I had posted on the social network Twitter, which was deemed to constitute a bomb threat against Robin Hood airport in Doncaster: "Crap! Robin Hood airport is closed. You've got a week and a bit to get your shit together otherwise I'm blowing the airport sky high!" You may say, and I certainly realise now, it was ill-advised. But it was clearly frustration, caused by heavy snowfall grounding flights and potentially scuppering my own flight a week later. Like having a bad day at work and stating that you could murder your boss, I didn't even think about whether it would be taken seriously.

Call me naive or ignorant, but the heightened state of panic over terror issues was not something I considered as relating to me in any way – until I was arrested, shoved into a police car in front of colleagues, hauled off to Doncaster police station, and interviewed for the rest of the day. My iPhone, laptop and desktop hard drive were confiscated during a search of my house. It was terrifying and humiliating.

I never expected to be charged, but a month later I was: not under the offence of making a bomb threat, for which I was originally arrested, but under the communications act for the offence of sending a menacing message. This first appeared to be an absolute offence, much the same as speeding: conviction does not depend on mens rea. For a stupid mistake, I was faced with the prospect of a career-ruining criminal conviction. After fresh legal advice it turned out I could argue I had no intention and awareness to commit the crime, and I could plead not guilty. Even after all the preceding absurdity and near-breakdown-inducing stress, I was confident common sense would prevail in my day in court.

Unfortunately,yesterday I was found guilty and ordered to pay £1,000 in fines and legal costs, which I have to find along with my own legal costs of another £1,000. I am considering an appeal, though I have no means, having left my job due to the circumstances.

The bright side has been an outpouring of support on Twitter, unexpected and overwhelming, with many users – including Stephen Fry and Jonathan Ross – offering to cover or donate towards my costs via a fund set up by a third party. Writers Sali Hughes, Emma Kennedy and Graham Linehan were among more than a thousand others who sent messages after my verdict was announced. Right now I'm unsure whether to accept their help, but I am truly warmed by the offers.

Whatever happens now, I remain terrified. Terrified of speaking my mind, terrified that my life has potentially been ruined. Most of the authorities could see it for what it was, and yet I find myself with a conviction because the Crown Prosecution Service decided it was in the public interest to prosecute. It would appear we live in such a hyper-sensitive world that we cannot engage in hyperbole, however misguided, without having civil liberties trampled on by, at best, heavy-handed police.

I would have fully accepted the police coming to my house to question me; it would have taken all of five minutes to realise what had happened. I would have learned my lesson and no taxpayer money would have been wasted on a frivolous prosecution. I have had some very dark days, and my family has been put through the wringer, because I made one silly joke.

twitter.com/pauljchambers