I think we should be quite clear about one thing here: if you're serious about boycotting countries on the basis of flagrant human rights violations tolerated or actively committed by their governments, a pretty good place to start would be most Islamic countries. (OK, so to be totally fair, an even better place to start would be 'most countries', but it's Islam that much of the outside world seems to be either vilifying or championing at the moment.) No doubt in some people's eyes this makes me a horrific racist imperialist Islamophobe - but isn't that just the same straw-man argument whereby the Israel-boycotters accuse anyone not in favour of punitive measures against the country a "pro-Zionist" who thinks they (the boycotters) must be raving anti-Semites? In fact, isn't that a second-order straw man? *head asplode*
HMLT's posts, in this thread and elsewhere, merely confirm that for a certain segment of the modern Left (or 'Left'), Arabs and Muslims in general are now somehow beyond criticism. This seems to be because some Muslims - in Palestine, Iraq, Guantanamo - are suffering at the hands of the either The Great Satan, TGS's most loyal lapdog or New York's funny little Hebrew-speaking outpost in the Levant; this is obviously a Bad Thing, yet the huge number of Muslims being killed or mistreated by their fellow Muslims elsewhere somehow seems to fall beneath the radar. So it's OK if they do it to each other, is it? What about if they do it to black Africans? Some on the pro-Muslim left have gone as far as to say that calls for UN intervention in Darfour are due to "anti-Arab bias", since it's Arabs that are dispossessing literally hundreds of thousands of black Sudanese, many of whom are in imminent danger of starvation or disease, or have already died. This humanitarian crisis, by any stretch, dwarfs* what's happening in Palestine, so why are the Palestinians a cause celebre while the Sudanese die in their thousands while the world sits on its hands?
I should say at this point that I think the level of criticism Israel draws from left-wing groups around the world is not, in my opinion, fuelled by anti-Semetism. I think it's a by-proxy form of anti-Americanism.
Edit: with regards to this particular proposed boycott, I will say that if a serious analysis of the situation (by someone with a far greater knowledge of it than me) can realistically say it has a good chance of forcing positive Israeli action towards the Palestinians - not merely an infantile "what's bad for Israel must be good for Palestine" knee-jerk, which is obviously untrue - then I would support it.
*200,000 - 400,000 dead since 2003, 2,500,000 made refugess, according to the Wiki article.