He was responding to Sarah Sanders who used the phrase "known or suspected terrorists" when trying attribute this risk to the southern border
Wallace then tried to fact check her, saying (and I am paraphrasing) 'this isnt just the border, it includes- and is in fact MOSTLY- at airports.
THE KEY is that Sanders used "suspected"...this means anyone on the TSA watch list that is engaged by TSA, is by definition "a suspected terrorist".
How many get arrested? 4? 40? (Oooh, better keep this secret, 'operational blah blah blah'.)
The title of this thread is (still) inaccurate. Wallace did not say they were all terrorists. He referred to Sanders 'known or suspected" categorization, he never called them all terrorists.