I would not go so far as to say that councillors (or any other politicians) should not change their minds. There is a balance to be struck between being responsive to new information that arises after being elected and being true to commitments that were made to voters before being elected.
There is a social contract of sorts between elected politicans and voters. To give a glaring example, there was something not quite right about Dave Emerson being elected as a Liberal then two weeks later, presumably after thorough consideration of new information, deciding that really he is an avid supporter of Harper.
Gordo may have some good reasons for introducing the HST and taxing items that have been PST exempt, but why didn’t he tell us that three months ago before the election? HST has been on the table for several years - it didn’t exactly come out of the blue.
When politicians change their minds they may have good reasons for doing so. Another possibility is that they did not do their homework when they committed to a platform. A third possibility speaks less well of their motivations