In a redraft, I would definitely veto. Smoltz is having, and looks like he will continue to have, a year equivalent to Hamels. And I'm a big buyer on Francouer this year... he could be a top-20 OFer.
In a keeper league, I let it go. I didn't get Smoltz in any league because he has to get old eventually (you would think, anyways) and Hamels could be a stud going into the next five years. So it depends kinda on league settings (slots/categories/etc) and how the keepers are structured (keep 3, keep 7, keep at whatever pick, whatever, whatever), but as a generic answer, I can see value equivalence, or at least close enough.
Even though I defend the right to veto trades, I only think it's appropriate where it's truly, truly bad. And this isn't.
0-3 to 4-3. Worst choke in the history of baseball. Enough said.