If timestamps were not validated, I think it actually would be a problem because attacker could build a very long chain very quickly and broadcast that whole chain.
No, the attacker cannot build a longer chain. Re-read my
first post, I don't know how to make it any clearer.
I see your point now, sorry... but still I think there could still be problems.
Why wouldn't the network build on top of your long chain since you were the first to broadcast it?
Also, it would be a very chaotic situation if you had miners trying to solve at different
difficulty levels. A lot of reorgs. And a distinct possibility someone would come out with
X number of cheap blocks. Such chaos would be very bad for Bitcoin.