Very easy as it seems

First of all - you'll need to engage person in an conversation
During conversation - liberal democrats will show them self inadvertently

First what you will notice is that you are being taught how to do things - This is the first indication that you are dealing with an libdem (majority of them do not accept opinion that they do not like)

Second - at any attempt to disagree with this person -
you will feel that you are being attacked
(it can be expressed in extensive amount of "prove" info or simple insults to your address)
Basically - person would try to gain your attention back - by providing large amount of info (links, or copy/pasted articles) or simply shaming you for something (very common tactic !!)

Third - when libdems in minority they do not rise the voice - somehow those dudes work only in packs