Huh? Secure against ordinary 51% attacks and against 1000x attacks are two different things. 51% is possible. It isn't cheap or easy, but possible for someone with significant resources.

Monero's hash rate is probably >1/1000 of Bitcoin when adjusted to equivalent energy. It is quite secure against 1000x attacks, especially considering they are not entirely effective as they were against some gen 1 alts. Algorithmically it is reasonably secure against 100x difficulty spike attacks (as are most other current alts such as Dash), though somewhat better than those that don't have a variable blocksize (again such as Dash) to absorb a transaction backlog.