There was once a time not too long ago when if someone said "I want gay marriage", everyone would jump on the attack. Similarly for the rights of Aboriginals, or to stop slavery, or in support for interracial marriage, etc. etc.
Society eventually moves towards what is right for these social issues, it's a shame that some people can't accept that by being stuck in their archaic views of how everyone should be.
A more broad point - nobody is going to come and arrest you for being opposed to same sex marriage - or even outright homophobia. What you don't have is the right to have other people accept your views. This is not an abstract issue for LGBTIQ+ individuals. Some of them get, understandably, agitated when you advocate for denying them equal rights.
To put it more bluntly - you can say what you want, but you have to wear it.
While I respect what you say and the grounds you present in support of what you have said, I doubt that an MP can accurately represent his or her electorate with a single vote (not in/in favour), hence my suggestion of a general vote. Fair point about the constitution v. legislation though.
Edit: what I should have said was that when you last voted for your local member, none too few of the candidates expressed their views on same sex marriage at the time of voting (from what I recall, this was the case in my electorate at least), so how could they possibly make a decision with everyone in mind? Not possible. I say this because what we are discussing is an important and charged societal issue, which needs to be resolved as best as possible. I don't want to be hearing the same discussion in 5 years' time because we didn't get it right the first time.
Again, I largely agree with what you are saying, especially the bolded part. I'm just not a convert, especially after the commercialisation of the "je suis Charlie" thing. Plus never underestimate the naïveté of some people out there (you never know who's changing their profile picture thinking that it'll actually do something substantial)!
I think this will be an 'agree to disagree' thing.
The individual voting for a representative in a representative democracy is inherently making a compromise. Few people will vote purely based on a single issue - it'll be weighing up several issues and then choosing a candidate (or, much of the time, a party) that they agree with the most. It's the job of the politicians to act on behalf of their constituents, although they can never represent all of them. Sometimes - you need to make an unpopular decision (although supporting SSM is hardly unpopular).
I kind of got a bit wordy there, but I guess my point is - in our system, it's the job of parliamentarians to make contentious - even unpopular - decisions. They have the power to do it, and they should do it.
(On a tangent - I'm pretty skeptical of it, as most of the people calling for a plebiscite or a referendum are opposed to SSM - not saying that you are, personally).
As for Charlie - yeah, I pretty much agree. I guess I see it as pretty harmless (rainbow display pictures) - if not a little beneficial, so I can't really work myself up over it.
Same sex marriage is legal in the US and terrorist attacks happen in France and Tunisia. Coincidence? I THINK NOT.
http://www.tylervigen.com/spurious-correlations