I think you need to do both.

You can react and respond however you choose to, but its important to remember to be respectful about what you say. There is a middle ground. Say what you think, but do it in a way that means that others will (hopefully) receive it well. And if you can't say it respectfully, then I'd probably think why you would need to say anything at all (unless of course the poster has asked for a blunt, no holds bars, repsonse, and then go for your life I suppose).

Does that makes sense?