Is it legal for congress to question those accused of tresping?(Tareq and Michaele Salahi)?

I watched the video's that went up on Yahoo!, and I was wondering whether this is even legal, and if it is appropriate or legal to blatantly say (as Mr.Lungren) the "constitution protects fools, the constitution protects stupidity...", and whether the Salahi's were legally required to be lectured by them, don't get me wrong I'm not protecting nor condoning their actions, I just want to know where legality stand's on this.