“Why did Southerners attack New England for talking secession during the Jefferson administration and the War of 1812? Didn’t they believe in “states’ rights?”
Was there a war launched against New England to force them to remain in the union?
No, because they never got any further than grumbling about among themselves a little bit, then dropping the idea. Nevertheless, the Democrats attacked them for treason in even thinking about it and used it as a club to bludgeon the Federalist party to death.
Here's one Virginia newspaper editorial from 1814;
"No man, no association of men, no State nor set of States has a right to withdraw itself from this Union, of its own accord. The same power which knit us together can only unknit. The same formality which forged the links of the Union is necessary to dissolve it. The majority of States which form the Union must consent to the withdrawal of any one branch of it. Until that consent has been obtained, any attempt to dissolve the Union, or obstruct the efficiency of its constitutional laws, is treason-treason to all intents and purposes."
Neither was there a war launched by New England in 1812.
If they had launched such a war, it would have been and should have been suppressed as an insurrection.