How do you address the second paragraph in his answer?
Because that's already the case, not a 'could have'. You can't force someone to speak. You can't beat an answer out of them. They already can simply choose not to answer and yes, it is up to the government to prove they aren't a citizen before deporting them (although they constantly fail at that, even with the bureaucratic nightmare we have now).
The answer is not either extreme. We don't need months or years of courts and paperwork but we also don't need to just strip out rights and become exactly what we became a nation to get away from. With current technology and biometric identification, it can be much easier to expedite the process. It may not be as fast as some want or 'shoot them on sight' as some want, but we always should err on protecting individual rights.
What if the person wasn't just unwilling to speak but couldn't?
There are many cases like the George Jimenez case- a legal US citizen who was mentally disabled. He was picked up on a simple trespassing charge but got caught up in the legal mess of rapid deportations under Obama (even with all his liberal policies). It wasn't that he refused to answer the questions, it was that he simply couldn't even understand them in the first place.
Even with all of Obama's liberal policies, he was deported and only was 'rescued' (for lack of a better term) when a church in Mexico found him homeless and tried to help him.
So even with all the 'bleeding heart' liberal policies, that US Citizen was wrongly deported. What happens if we strip away any due process?
I'm sure some will say it is 'good for our gene pool' and he was just 'too stupid'.