I can only assume you have not talked with antivaxxers, climate change deniers or people taking their religion too seriously.
Whether insult hurts or not is your choice. If you have such weak control over your inner world - learn to not give a fuck. not that hard.
This is nonsense. If you are subjected to continuous, vitriolic, realistic rape threats on Twitter then this is inevitably going to stress you and make you feel somewhat unhappy or unsafe. But if you are a 14-year-old, or otherwise particularly vulnerable, then they may cause acute depression or suicide.
This Act isn't about antivaxxers or climate change deniers. It is about revenge porn and vicious cyberbullying, and I am not prepared to stand up for either.
The problem here is that most people who suggest 'just ignore it' as a solution haven't ever faced the sort of abuse that the proposed law is designed to deal with. You're quite right that it's easy to ignore an insult. It's much harder to ignore a believable death or rape threat, racist remark, misogyny, etc. That is what you're suggesting people should 'learn to not give a fuck' about. As someone who believes quite strongly that we shouldn't just ignore those things and that we should actively try to stop them, I find your argument incomprehensible.
Because you can't know, until communication starts, whether it's going to be vicious. And you can't walk around with your fingers in your ears all the time.
Some internet services get this, but it's awfully easy for people to generate new accounts to route abuse through.
We could do well to develop anti-abuse technology in the same mode as anti-spam.