If someone uploads their library of child porn encoded to base64 split across tons of tweets, do you want Twitter to have a choice between removing that content and continuing to operate?
We have 3 options here:
1. No moderation allowed whatsoever on a site without a court order. That obviously leads to a terrible, toxic community with lots of reprehensible content that the average person wouldn't want to participate in.
2. A good faith effort at moderation. This allows the most reprehensible, highest-impact content to be removed and allows users to participate in the moderation process.
3. No content can be published without moderation, on any site anywhere. Want to post a Facebook status? Have fun paying $20 for the privilege of waiting 48 hours for a human to review it.
All of this is irrelevant though, because this executive order is not targeted at censorship. It's targeted at a private individual who voluntarily, for free, passed on a message from one person to many other people and decided to tell them "this seems fishy, you might want to read up on it."