There's a quote doing the rounds of Methodist circles which I assume is genuine. It's from the diary of John Wesley (naturally) and reads: 'I met those of our society who had votes in the ensuing election, and advised them, 1. To vote, without fee or reward, for the person they judged most worthy: 2. To speak no evil of the person they vote against: And, 3. To take care their spirits were not sharpened against those that voted on the other side.'

The 'society' is Methodists, of course, and it's worth adding some historical context. This entry was for October 6, 1774, a long time before Britain was a democracy in anything but name. There might only be a handful of electors for each seat, meaning bribery and corruption were routine – not to mention intimidation and bullying. Violence at hustings was common, particularly as the candidates would make sure their supporters were well lubricated with ale. This particular election was significant, too, though Wesley wasn't to know: it saw the return as prime minister of Lord North, whose arrogance and incompetence sparked the American War of Independence.

Politics in the 18th century was notoriously brutal, with cartoonists like Gillray, Rowlandson and Cruickshank creating bawdy, scurrilous and often disgusting caricatures of political figures. And with the advent of the internet, it's all come back.

One of the most depressing things about the current general election campaign is the amplification on social media of our worst instincts. The tribalism to which we're so prone is unleashed, and things are said, by good Christian people, that really don't stand up.

Here's the thing. I don't think Jeremy Corbyn is a good leader of the Labour Party and I don't think he'd make a good prime minister, but I don't think he's a fool, or a criminal, or unpatriotic. Most of what he says I actually agree with, and checking what the right-wing press says he says against what he actually says leaves me with the feeling of inhabiting a parallel universe.

I don't vote Tory, but I think Theresa May is, on the whole, playing a bad hand as best she can. I don't judge her for calling a snap election when she said she wouldn't. As Keynes once blisteringly retorted to similar criticism, 'When the facts change I change my mind. What do you do?' She might be wrong about stuff, but she isn't a hypocrite. And by the way, the fact that you vote Tory doesn't necessarily mean you don't care about poor people, as one widely shared meme suggests – it might just mean you have different ideas about how to help them.

Speaking of hypocrisy, that's a charge that's been levelled against the Liberal Democrats ever since they went into coalition with the Tories. It's stupid, so just stop it. The country was looking into the abyss, and they took brave and costly decisions to help pull it back. Of course they compromised, but compromise is not hypcrisy. And as for those attacks on Tim Farron for his views on homosexuality – don't get me started. 

When I see Christians I know and respect repeating mindless slurs on the character and policies of their political opponents in all seriousness, I think a little Wesley might be good for them. Don't speak evil of your enemies. Don't let your spirits be sharpened against them. They are, on the whole, decent people trying to do their best.

Does that mean politics has to be bland and nice? Not a bit of it. I'm all for passionate engagement. It's our opponents as people to whom we owe respect; to their weak, dangerous arguments, unworkable policies and bankrupt philosophies we owe none at all. We ought to be able to distinguish between the two, and vote, without fee or reward, for the person we judge most worthy.

Follow Mark Woods on Twitter: @RevMarkWoods