All the tech companies should stand together and be ready to block access to their services. Imagine if the UK was left without access to just WhatsApp, let alone iMessage etc. It's not irresponsible or unsafe, there's always SMS for which the govenment has full control over.
Also I don't think any of these companies should fear an competitors. Why? These services are so ingrained a few weeks if not months of protest will not change anything. When the govnement finally succumbs restoration will be easy and the numbers will go back to normal quickly.