Hamas is a designated terror organization. As such, it's illegal for them to have a Twitter account. It's also a breach of Twitter's own Terms of Service. See here for a comprehensive explanation: http://blogs.timesofisrael.com/kick-hamas-off-twitter/
It is illegal for a US citizen or company to provide an FTO:
"…any property, tangible or intangible, or service, including currency (…) lodging, training, expert advice or assistance, safehouses, false documentation or identification, communications equipment, facilities, weapons…"
A Twitter account is an account to access and use a service provided by Twitter, you are a US company based in San Francisco, California. It is a federal offence to provide Hamas with services. As a US company, you, Twitter, are breaking the law by providing Hamas with a Twitter account.
Further, you, Twitter, have comprehensive Terms of Service (TOS). Hamas’ use of Twitter breaks your own Terms of Service in a few ways:
Section 1 of Twitter’s TOS says:
"You may use the Services only if you … are not a person barred from receiving services under the laws of the United States"
As mentioned above, Hamas is banned from receiving services under US federal law.
Your Twitter’s Rules (a part of your TOS) also specifically ban:
"Violence and Threats: You may not publish or post direct, specific threats of violence against others."
Hamas has used the Twitter account to threaten Israeli soldiers, leaders and civillians
"Unlawful Use: You may not use our service for any unlawful purposes or in furtherance of illegal activities."
Hamas is using the account for a variety of purposes illegal in the United States: Promoting itself (a designated FTO), promoting terrorism, promoting the firing rockets at Israeli cities (a War Crime) and probably more.
"Twitter maintains the absolute right to kick anyone off of its services for any reason, but especially for those who either break its TOS or expose Twitter to possible legal action."
Both of these are true of Hamas.
I'm asking that you act legally, ethically, and not in contradiction to your own standards set in your Terms of Service.
Delete all Hamas accounts immediately!