If a 19 year-old college student can get a fake ID to drink, why couldn’t a bad person get one, too? And no matter how sophisticated the security embedded into the ID, wouldn’t a well-financed terrorist be able to falsify that, too? The answer to both questions is obviously ‘yes’.
Honest people, on the other hand, go to Pro-Life rallies. Honest people go to Pro-Choice rallies, too. Honest people attend gun shows. Honest people protest the actions of the President of the United States. Honest people fly to political conventions. What if those with the power to put people on a ‘no fly’ list decided that they didn’t like the reason for which you wanted to travel? The honest people wouldn’t be going anywhere.