not mentioned? Why would Elizabeth not mention it in the course of her conversation with her father if it was known? Yes, it is a conjecture. I'll revise my statement and say that we know of no other objectors. There could have been gossip among officers and neighbors saying, 'I can't believe Lydia Bennet's father is letting her go!' But even in the absence of knowledge of anyone else's objections aside from Elizabeth's, seeing Mr. Bennet's past behavior towards his daughters, and Mr. B not knowing some of the information Elizabeth does, IMO I don't see that Mr. Bennet is acting any more or less responsible than he's been represented as a character thus far in the book.