There were a lot of great replies, but what I loved most was a response from someone who went by "Zmark," who wrote back --
"Since we r nation of laws, you should know the Constitution ALLOWS the President to act alone in certain circumstances."
To be clear, I don't mind at all if Rand Paul or any other Republicans in the Senate disagree with the president's views and actions. I just like them to at least know what they're talking about and not just pander to their base with quips that sound like they're meaningful, but are empty.
By the way, related to this was another reply that said -- "then help him out act with him."
Obviously, Rand Paul has no obligation to act with the president if he disagrees with the action. But the point is that he wasn't complaining about the president's position, just that he acted alone. If in fact he agreed with the general principle about whatever action the president had taken, but just bothered by some details and that he'd done it alone, then indeed Sen. Paul should have reached out to try to find a compromise and act with him, rather than merely whining disingenuously about taking an action alone.