S/he's not saying you're an awful person or that you shouldn't be allowed to play how you want though. You just said that Quelling Strikes "makes little to no difference", while Blowfin (quite rightly) suggests that it can actually be an indirect DPS boost situationally as it prevents you having to moderate your threat (and in doing so, lose DPS).

You do realize that partying is a team effort, right? It's not always about putting out the big numbers, sometimes not putting out the big numbers can be every bit as helpful. You have to gauge the situation to see if going all out is a good idea or not. And if it's not, then it's just as vital that you don't. People have this idea in this game that DDs are balls-to-the-wall idiots that ignore the party situation and your comments don't really dissuade this viewpoint. I mean, this very thread is based on that view...
It is a team effort, and a DPS's role within that team is to do the maximum amount of damage possible without failing a mechanic, dying, or pulling threat (normally). Therefore, you want to be pumping out as much damage as possible without failing in one of those three ways - and Quelling Strikes is a great boon to the last of the three.