The "real reason" people "freaked out" about Trump dismantling agencies is that he was and has been ignoring the law by fiat and not executing the law as is his constitutionally defined role. It would be one thing to veto a refunding of the DoEd, to approve a dismantling of the DoEd; it's another to unilaterally dismantle institutions that have been enacted into law by Congress. The DoEd is no more unconstitutional than the DoD or any other cabinet-level institution.

I think it's fair to have a hard discussion about the effectiveness of or need for the DoEd, but the way to do that is in Congress, not by fiat by the president. The way the Trump administration has approached it IMHO is grossly unconstitutional and a violation of the separation of powers. The only semi-reasonable rationale I can think of is that Congress is implicitly approving of or voting on the president's actions by not impeaching him, but that seems like an unreasonably high bar, equates lack of action with active approval, and it also infringes on the power of the Congress that enacted the law.

As someone else here on HN noted recently: what is the point of anything pertaining to congressional vote procedures, veto authority, overrides, and so forth if the president ignores, and is allowed to ignore, the laws that are passed anyway?