As a general rule, don’t answer personal attacks or aggressive comments, but you might have someone from your team counter them calmly and factually so that when someone just scans through comments, they are not all or mostly negative. When someone from your staff does this, they don’t have to identify themselves as part of your team but not deny it either.
Delete and block anyone who is out of order or rude – get rid of them. If they are aggressive or threatening, contact law enforcement. As a rule, make screenshots of all comments you delete, so that if it should ever become an issue, you can look up why you blocked them. Don’t waste time battling the trolls on the internet, they feed on the attention.