Wrong. 5...Nxd5 6.Nxf7 is actually OK for Black, although the position is quite complex. The only real problem is the Lolli (6.d4!) where Black is somewhat worse, but he can pull a few rabbits out of the hat.
5...Na5 is a cleaner solution, and after 6...Bb5+ Black can pick either the ambitious 6...c6, or the solid 6...Bd7. IMO both are perfectly adequate.
5... Na5 leads to an unclear game, though White will be a pawn up.
5... Nxd5 seems very dangerous after 6. Nxf7.