Should Twitter remove abusive tweets?

Twitter is almost 10 years old and throughout its existence it has struggled with the issue of removing abusive content. Officially, the micro-blogging platform says it does not moderate content and does not interfere with freedom of expression. However, it appears Twitter has filtered abusive tweets in the past. Buzzfeed claims it did so when it came to a 2005 Q and A with US President Barack Obama. Twitter's former CEO denies the claim.