"what they were doing" is attempting to illegally abduct someone. The comptroller's "impeding" was a demand to see the one thing that would make their request a legal arrest.
Instead, they arrested the comptroller without even a pretense of the law.
In many situations, they just need a documentable/articulable (to a judge, later) reasonable belief that a crime was occurring in their presence, or in other situations that a specific crime had occurred and there was a reasonable belief that person had committed that crime.
Resisting arrest, and impeding official business of a police officer are usually arrest-able offenses almost anywhere.
Details vary by jurisdiction and crime, but ‘you need a warrant to arrest someone’ is an edge case, not the common case. In those cases, it’s also often an indictment or bench warrant.
If we normalize some dude in a mask and a baseball cap as someone that has the authority to arrest you and put you in an unmarked van, that represents a real and serious breakdown of trust and order in society.
ICE agents should wear a real uniform (ICE with their real name), have uncovered faces, and be required to show badge/authorization upon request -- otherwise members of society have to reason to trust them (or people who look like them).
Maybe he was right to do so, maybe not, but it had nothing to do with "asking a question".