Check your country laws, but it's likely that either:
They have to pay you for the time they want to have a say over your work; or
This clause is probably illegal;
If your side projects aren't related to their business, they can't claim anti competition grounds. And if they're not paying for your time, they can't have a say over what you do with it, as long as what you're doing is not illegal, risks damaging their reputation or their business.
If your projects are related, but not really competing, a way around might be teaching other people. Publish your code and instructions. Having educational purposes helps to rule out any intentions to compete against them and you can argue that teaching is a good way of learning, as is widely known.
Look for a lawyer to get professional advice, as I'm not one.
risks damaging their reputation or their business.
This is probably their main concern. If everyone knows John Doe works for ABC and John writes some pretty horrible code that could end up looking very bad for the company.
Even worse, if John Doe contributes some code with obvious security holes one might think to try some specific attacks against ABCs apps.
In both of these situations, ABC might want to talk to John and give him permission about which projects he should be contributing to.
Otherwise, create an anonymous GitHub, do whatever you want, if you quit or get fired change the GitHub name to your real name (surprise! it was me John all along! muahaha) and then call their bluff on the lawsuit part.
I was thinking more about profanity, obscenity, getting involved in violent extremist groups, or the like. I wouldn't want an employee contributing to web apps related to KKK, Antifa or anything violent such as. But that's more about whether the person fits the company culture or not.
Although I get your point of view, I still don't think it should be grounds to limit what an employee can or cannot do in their free time.
What the company could state in their contract is: "You agree that we can monitor your public projects and contributions to open-source. The code contributed publicly can be used to assess your performance and continuity of the contract with Company XYZ".
That would be reasonable and acceptable.
Becoming a toll to proactively limit what the person can/cannot do is unacceptable. An employer is hiring hours of his time, not his life or free will.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
Check your country laws, but it's likely that either:
If your side projects aren't related to their business, they can't claim anti competition grounds. And if they're not paying for your time, they can't have a say over what you do with it, as long as what you're doing is not illegal, risks damaging their reputation or their business.
If your projects are related, but not really competing, a way around might be teaching other people. Publish your code and instructions. Having educational purposes helps to rule out any intentions to compete against them and you can argue that teaching is a good way of learning, as is widely known.
Look for a lawyer to get professional advice, as I'm not one.
In both of these situations, ABC might want to talk to John and give him permission about which projects he should be contributing to.
Otherwise, create an anonymous GitHub, do whatever you want, if you quit or get fired change the GitHub name to your real name (surprise! it was me John all along! muahaha) and then call their bluff on the lawsuit part.
I was thinking more about profanity, obscenity, getting involved in violent extremist groups, or the like. I wouldn't want an employee contributing to web apps related to KKK, Antifa or anything violent such as. But that's more about whether the person fits the company culture or not.
Although I get your point of view, I still don't think it should be grounds to limit what an employee can or cannot do in their free time.
What the company could state in their contract is: "You agree that we can monitor your public projects and contributions to open-source. The code contributed publicly can be used to assess your performance and continuity of the contract with Company XYZ".
That would be reasonable and acceptable.
Becoming a toll to proactively limit what the person can/cannot do is unacceptable. An employer is hiring hours of his time, not his life or free will.