... condemn Denny on a couple of comments, I can see a possibility that
Denny (who had renewed a slight acquaintance (ch. 35) in bringing Wickham to Meryton) has lost respect for him in the ensuing months, especially at Brighton
Wickham, rather openly extravagant (after all Col. Forster knows enough to say (ch. 46) he's not a man to be trusted, is also rather openly a rake (all Meryton admits knowing it after the elopement), and Denny knows it
Upon hearing of the elopement, Denny simply sneers, "huh! I don't believe he'll marry her!"
Accosted by Col. Forster, Denny denies, truthfully, knowing anything about the elopement beforehand or anything of Wickham's intentions
Same references as yours, totally different inference. I don't deny your inference; I simply recognize it's not clear-cut, and we don't have a solid reason to call him a coward or anything else bad.