In the abstract sense I suppose a point is being made but it isn't very weighty given its disregard for proportionality and context, among other things. It's a deep and not obvious question of moral philosophy - is violation of human rights a per se wrong, or is it wrong only in certain contexts? It's the same issue as the debate over torture - is it justified in some cases? Given the level of depth such a question requires, I don't think any progress could be made on it in a forum like this.
I'm mostly on your side in this, but I think there are reasonable questions being asked of you. Is the risk of listening in on an innocent conversation as serious as the risk of wrongly convicting someone for a crime? Morally and ethically, are they of the same magnitude? Please note that this is different from the question of whether government should be given carte blanche power to listen in on innocent conversations just in case it's able to come across information that prevents a nuclear attack. I agree that it should not.
True enough that a violation of the Constitution is a violation of the Constitution (and I'm inclined to think it was violated in this instance). But are all violations really the same from a moral perspective, regardless of the circumstances? I guess that's what this issue comes down to. My view is that they're not all the same.