Something awful happened to me last week while I was playing Grand Theft Auto 5 (GTA). As usual, I was hijacking a car; either because I wanted to escape the police or because my other car was parked about 50ft away and I couldn't be bothered to walk over to it. It doesn't matter which.

However, this time the driver happened to be an old lady. A sweet old lady who pleaded with me not to hurt her as I pulled her frail body from her seat. That car was probably the only thing that still allowed her some degree of independence, I realised. The insurance company would probably dick her around, too. It might take her months to get the car replaced. And that's if she even had the confidence to return to the wheel at all, which she probably wouldn't.

Robbing the old lady, even though I knew she was just a lump of pixels, made me feel terrible. What sort of monster had I become? Appalled at myself, I gave her the car back and let her drive away in it.

I am rubbish at GTA 5. I think I'm just a bit too Guardian for it.

There have been other instances of this. I've only ever robbed one shop, and that was only when the game made me. I won't do it willingly due to a misguided belief that you should support the local businessman. I routinely get shot dead on missions because I don't like the idea of topping up my health meter with sugary snacks made from processed foods. I'm barely even skimming what the game has to offer, and it's all because I'm a woolly, liberal, cartoon joke.

This sounds like comic exaggeration, but I promise it isn't. If the game controller's R3 button allowed you to leave an apologetic note on the windscreen of the car you've just accidentally bumped into, then that's how I'd spend 95% of my time.

It wasn't always this way. When the first top-down GTA game was released in 1997, I was as recklessly immoral as they come. Back then I'd quite happily flamethrower a line of dancing Hare Krishnas for a giggle. But now that I've grown up into a hand-wringing, left-leaning ninny I've found myself trying to play the game as responsibly as I can. Like someone's mum would.

Playing GTA Online only makes this worse. The story mode makes you do a number of terrible things but that's fine because you're controlling a fictional character. But online, when I'm controlling a character who looks like me – albeit a skinnier, more attractive version of me – everything changes. For want of a better word, playing GTA Online turns me into a yellowbellied nancypants.

I'm pretty sure I'm alone in being crippled by this sense of social responsibility, too. When you play GTA Online, you can hear everyone else, and in my experience all the other players are either rapping six-year-old French arsonists or middle-aged men who only stop trying to murder me as gratuitously as possible in order to shout swearwords at their newborn babies.

And yet, despite all this, I'll keep playing. Because the beauty of GTA is that it's set in such a perfectly realised world that nobody ever has to compromise their ideals if they don't want to. There are plenty of other things to do within the game. So let's hear it for GTA 5: the most expensive biking around a mountaintop while listening to Eddie Murphy simulator that there has ever been.