Do I have to respond to every negative comment on social media while marketing my product?

Yes. I really like it when negative comments about a product shows up on a brands social media. For one reason, it makes the brand more believable -- that some people will not be happy with it. For the same reason, I really distrust brands that have no negative comments about their products.Negative comments about a product gives you two opportunities. The first is the valuable feedback it offers and how you can improve your product based on your consumers. The other one is how to set up the personality of your product based on how you answer the negative comments.

Yes It is very important to respond to negative comments specially by offering them solutions of the problem they faced or explaining the reason why they had bad experience with our product and you should even explain your business model,rules,limitaions to customers who are notoriously commenting negative that will be helpful for other customer to understand your position.