It's ironic you quoted that when, as pointed out by Nikki, Lampard proceeded to sign a few not-quite-tall players.
Did I say height is not important at all? It is important and it is important to have some tall players in the squad but it is not the be-all and end-all. A player can be tall but if he's shit physically, then there is no point. Equally, a player can be short (and I don't mean super short) but if he has great leap and/or is strong physically, then he can be useful.
Moreover and again, am not saying height is not important, but I feel like the height factor mentioned by Lampard was just an excuse used by him to cover up for his poor set piece defending organization. Remember Azpi marking Soucek (IIRC) while Abraham was guarding the post for the first goal in the loss to West Ham? This was already an issue with Lampard at Derby and it suggests the main problem here is not the height...