Re: no one is forced to use twitter or facebook.
Nor are people forced to have a website or an email address. However, it's increasingly difficult to function, especially if you're self employed, for example, without the use of social media.
If you remember some of the examples given as to why being forced to use your real name on Google+ (also Facebook) was bad then it follows that any breach of your privacy on social media is just as bad. The most recent example being the disgusting doxxing attacks carried out in the pursuit of "ethics in gaming journalism" *cough*.
It's not as simple as "I'm being harrased/stalked/bullied on Facebook, I'll just move to Ello instead".
Remember, also, that in some cases the cyber bullies are also those same bullies you can't avoid at school.
The reason the medium is relevant is that Law relies heavily on wording and Case Law. When the medium changes to something new that wasn't thought about in the original draft and/or has little to no case law to go on, there's essentially little to nothing to go on in order to bring a successful prosecution. There's also the difference in scale. If BT erroneously publish my telephone number in the business directory when I've opted out of the residential phone book then the potential privacy breach is maybe the tens of thousands (no idea, just pulling handy numbers out of my arse for illustrative purposes) but if someone sticks my number in a public post on Facebook to invite harrassment or otherwise to cause me grief, then the potential breach is the number of people on Facebook plus anywhere it gets reposted (Reddit, Twitter, 4Chan etc...) and that's enormous. A potential that just isn't taken into account in current harassment laws.
So, in my opinion anyway, I think it does need either new laws or old laws being extended.