For individual websites with any form of participation, whether it has comments or full social media elements, the ethical limits users are allowed to cross should be made clear. For anyone who uses a dedicated server to host other websites, the same is also true, especially if you have a small reseller hosting company with limited access to legal counsel.
Issues like tobacco, firearms, alcohol, gambling, pornography, and racially offensive terminology are legal in many countries but may or may not be what you want to allow on your sites. As a private individual or company with ownership over your web space, you have every right to place limits on what can and cannot be done or said by users on your sites. This may even be solely for the protection of your commercial interests rather than political or moral motivation. Certain controversial elements can put your site or server in danger of malware attacks and negative media. Whatever standards you set, make them clear and be firm.