The Hammers boss was left angered and shocked by the woeful scenes that allowed Terry Venables' side to take a 4-1 lead before half-time, and described the goals conceded as 'pathetic'.
"The inconsistency of this team this season has been unbelievable," said Glenn. "The defending has been a lot better overall of late - we kept clean sheets at Fulham and Sunderland and have looked much more solid - and then we come out today and defend in a manner that is completely unacceptable.
"It wasn't a case of the players in the first half not being motivated. We started really well, the tempo was high, and Trevor Sinclair might have scored with a header from Paolo Di Canio's quick free-kick, just before we conceded that pathetic first goal.
"They were all pathetic, we have gifted Leeds four goals in the first half, and that is just something I can not legislate for. You can not win matches if you concede four goals in the first half, it is virtually impossible.
"The players did all they could in the second half to try and get something out of the game and, quite honestly, at 4-3 we had a number of chances to level the match but that wasn't going to be.
"The second half performance was encouraging, but we have got nothing from the game, and that is all that matters. We needed to take something from this match, but we haven't, and the result now just dulls the memory of the fightback in the second half."
Glenn also revealed that midfielder Steve Lomas, forced off with an ankle injury just after half-time, could now be out of action for a few weeks - hardly the sort of news we want to hear before our next game at Upton Park on Sunday.
"Steve Lomas has suffered a twisted ankle, it looks quite nasty, and that really is the last thing we need at the moment. We have Manchester United here next week and it goes without saying that we need to produce - for 90 minutes - the kind of performance we saw in the second half today."