"Your view is that this was done purely for the sake of not letting "brown people" into the U.S.? For 2 minutes?"
For more than two minutes.  They were only let out because of the lawyers and protesters.  
And yes this is about brown people.  It is about making Trumpkins who cannot even find Yemen on a map feel good about the US keeping out the people who aren't of my religion and have darker skin and make me feel uncomfortable for being different.  

"And that there is no need to have any immigration control, because the threat of terrorism is "imaginary"?"
Iranian preschoolers don't commit terrorism.  This does nothing to prevent people from being killed by terrorists.