I'm not seeing the "scientific arrogance" here anymore than just plain old human arrogance. How could we possibly conceive of alien technology or biology? We move forward with a basic set of assumptions that are likely wrong, but the best we can muster. Up until now lasers were pointless (pun intended) because they're so narrow you can't hit anything that it isn't directly aimed at; visible light is too easily blocked and as mentioned, quasars have given us false hope in the face of the "certainty" that it had to be an intelligent source.
The human arrogance assumes a lot of things about life and sentience elsewhere. It assumes they care enough to look, it assumes they're curious or unencumbered by religious beliefs that allow them to look beyond themselves, it assumes they have a need for technology, it assumes they're complex enough to develop it... Imagine a planet populated with creatures as beautifully complex as what inhabits 99.999% of our planet and then realize we're the only species here that would even know to look and we're just as likely to use that technology to do everyone in. :)
Just imagine when we shut off all of our radios and shoot data through fiber optics underground, that's a pretty narrow window for anyone to notice the "noise" emanating from our rock. I also imagine if probes showed up from a paranoid alien species we might be better off unnoticed before they clear cut our planet of pesky and potentially dangerous biological components in the quest for more resources....
Location, location, location. We got the best real estate deal in quite a distance, we better hoard this shit.