Say you're a publisher and a blogger criticizes you. Maybe they criticize your prices, or the quality of your work, or your sales tactics; it could be anything. How could you respond?
Reach out to the blogger. Let them know they're being heard. Change the way you do things. Try to address their concerns. Hey, no one's perfect right? Fessing up to a mistake can build serious goodwill.
This is the Internet. Sometimes people are wrong. You could write a patiently worded response that explains, in detail, why the blogger is mistaken. Maybe they'll change their mind, or maybe not. Either way you'll have participated in rational, open discourse.
Did I mention this is the Internet? You can ignore whomever. Just do your business & be happy about it. If you're really confident in your product, you shouldn't be that worried anyway.
There's one thing you probably shouldn't do, though: use legal action to censor public speech. Whether it's against the blogger, or their employer, it's not cool. Threatening to sue everyone who says something mean about you is unsustainable, childish, & misguided. You're not making your brand look better (quite the opposite, really).