Ignore it and delete it. Its an unfortunate fact that 95% of people on the internet are morons and there is nothing they like best than tearing people apart for their own satisfaction. Don't take what they say to heart, block the person and delete the comment. Eventually you'll fly through the negativity and it won't affect you.
What is best practice for if people leave negative comments on my blog or other social media platforms?
I like Anita's answer. There are gonna be haters however good you are. Just remember those who give negative comments are merely projecting their weaknesses.
Delete if it is just pure negativity but if it is constructive criticism take in on board and probably blog about it, addressing the issues and pointing out how the constructive criticism has added value to your enterprise.