Stephen Hawking is berated for traducing the spirit of free speech and liberty by boycotting Israel's upcoming presidential conference (Hawking boycotts conference in Israel, 9 May). According to the conference organiser, Israel Maimon: "Israel is a democracy in which all individuals are free to express their opinions, whatever they may be." But what sort of freedom of expression is it that condones and underwrites a state that "democratically" colonises another people's lands and imposes an oppressive occupation? I would have thought this was, par excellence, a case of actions needing to speak louder than words.
Alan Mackie
London
• Following the collapse of apartheid in South Africa in 1990, both black and white communities acknowledged that the international sport boycott had been more significant in the transformation than 42 years of "engagement". In Gaza and on the West Bank, the 56 years of engagement with the Israeli government since the occupation began has seen the situation worsen immeasurably for the Palestinians. Is not an academic boycott at least worth trying?
Michael Meadowcroft
Leeds
• I'd like to applaud Stephen Hawking's decision to boycott next month's conference in Jerusalem. I also find Shurat HaDin's comment (Hypocrisy claims, 9 May), that "if [Hawking] truly wants to pull out of Israel he should also pull out his Intel Core i7 from his tablet", to be utterly shameless. The virulence of the condemnation mounted against anyone who is critical of Israel's treatment of Palestinians gives the lie to claims that boycotts are ineffective.
Pete Stockwell
London
• Supporters of the boycott of Israel's academic institutions manifest inconsistency in many ways (Why Hawking was right, 10 May); here's a couple.
First – and most obviously – they should also be boycotting the US's academic institutions, given the horrendous treatment of Guantánamo prisoners – both immoral and illegal.
Second, they cannot deny that Israeli citizens have suffered horribly from Palestinian rocket attacks; presumably the boycotters strongly object to Israel's use of "collective responsibility" when retaliating and hence killing innocent civilians.
Paradoxically, though, the boycotters are themselves guilty of the misuse of collective responsibility – for they must surely know that many Israeli academics strongly oppose the Israeli government's policies.
Peter Cave
London