"On the issues - a question for CP; would you advocate taking similar action against John McDonnell? How about Ian Lavery? How about Ed Miliband? What are the criteria by which a Labour MP qualifies for this kind of direct action?" Ed Miliband certainly, can't say I've put much thought into the exact point at which a politician becomes an acceptable target. I don't think this kind of thing helps clarify matters that much - we could equally well debate what kind of response would be appropriate to use against UKIP, or a BNP stall made up entirely of pensioners, but the fact that gray areas exist there in no way invalidates no platform as a tactic. To turn your question around - would you be equally offended by action taken against a Lib Dem MP with Sir Meale's voting record? What about a Tory? If not, then what meaningful difference exists between those cases? Did the Right Honourable Lord Quentin Davies of Stamford suddenly become a legitimate part of the workers' movement when he defected from the Tories to Labour? Was it acceptable to heckle Lord Davies one day, but childish ultra-leftism the next?
I don't think this action will have done a tremendous amount to weaken Sir Meale's power (btw, you say it's "all well and good" to define neoliberal politicians as the class enemy, but you don't say whether it's correct or not - do you accept he has class interests opposed to ours? Or do you think he's still secretly a proletarian in some confused fashion?) but then most of the time protests don't have that much effect. If the recent wave of SPUC vigils had gone unopposed, it wouldn't have changed much, but I still think the people who bothered opposing them did the right thing, because reactionaries should be confronted wherever they raise their head. That principle holds true whether they're standing outside an abortion clinic or addressing a "labour movement" meeting. Anyway, I think we can agree that Sir Meale thought he would get some benefit from addressing this meeting, and he was denied a chance to put his politics across, and the more opposition and humiliation he faces when he attempts to speak in public, the less he's likely to want to do it. That, to me, is a contribution, however small, to weakening his power.
As for this stuff about the "labour movement", I deeply distrust the way the AWL uses that term, because it seems to be a sleight-of-hand whereby the working class as a whole is equated with the institutions of the Labour Party and the unions. Talk of "transforming the labour movement" smacks of alchemy to me, turning the TUC into the CNT or IWW seems about as likely as turning lead into gold. The key task right now is to find ways of relating to the vast majority of unorganised workers - the AWL like to dismiss attempts at alternative workers' organisation as being utopian and unrealistic, but the strategy of transforming the TUC and Labour Party seems equally unlikely. I don't think that heckling Labour politicians is the most worthwhile thing that anarchists are doing right now, that would be the anti-workfare campaign, but you seem a lot less interested in discussing that. And I don't believe that shouting at some politicians actually makes it any harder to try and organise claimants.
Finally (and I know this comment is already almost as over-long as it is belated), you talk about "shrill actions which will do... lots to earn you the hostility of the vast majority of organised workers". Let's break this down a moment: 1) as discussed above, most workers aren't organised. Let's stop talking about organised workers as if they were the same thing as the class, or even necessarily the most conscious elements of the class, please. 2) Assuming that by "organised workers" you mean "union members", I don't think that most union members were on the Nottingham May Day march. I dunno how many people were there, but this report estimates 200-500. Even if we assume 500 people were there, and every single one of them were angry at the anarchists, that's still a tiny proportion of organised workers, let alone the working class as whole. Unless you genuinely believe that those 500 people who turned up to Nottingham May Day are the vanguard of the class, I can't really see how mildly annoying 500 people sets back anarchist organising in any meaningful way whatsoever.