The need is to discredit his foreign policy 'position' and this no responsible politician has done yet by pointing out to its contradictions. Namely, that it can only facilitate the increase in violence in Syria, not affect the outcome and forestall the possibility of a negotiated peace.
The main insurgent groups have already rejected the National Coalition representing Syria politically, making the Geneva Conference all but pointless as Assad would have no group to negotiate with. He can then claim all the more that the insurgents are just 'terrorists' and the killing will go on at a more frenzied pace.
Either Hague knows this is the way the insurgent groups fighting against Assad work or he is incompetent. He's supposed to be a Conservative and yet he is prepared, in theory, to back The Revolutionary Movement in Syria if Assad does not cut a deal at Geneva in June ( which 'they' cannot or will not ).
The BBC reports,
'A statement issued by the Revolutionary Movement in Syria said the coalition had failed to represent the Syrian revolution.
The joint statement by four leading rebel groups inside Syria says the National Coalition for Syrian Revolutionary and Opposition Forces (SC) is unable to fulfil its obligations due to "ongoing discord".
A meeting of National Coalition members in Turkey has been marked by sharp divisions and a failure to agree on who should represent them at the June conference in Geneva. "This negativity," the statement goes on "has led to the blatant interference of international and regional parties without respect to the national will."'Presumably, even Hague can work out what the meaning of 'revolution' actually is and it is not merely the removal of Assad but to for them to impose their national will on any new Syrian government. The revolutionary guerillas believe they can go it alone and overthrow Assad without comprimise.
The Revolutionary Movement have been encouraged in that by first the indication from the US and UK might send arms to Syria. The largest indication yet that both the US and Europe could do so came with Hague's so-called 'diplomacy'.
As Britain and France have not ruled out supplying them arms, the insurgents fight to the bitter end in the hope they alone will then de facto represent the national will. This, of course, was the claim by all those post colonial secular dictators such as Colonel Gaddafi in Libya and the Assad dynasty now ruling Syria.
The insurgent groups in Syria reject 'interference' by 'international' and 'regional' parties that are against 'the national will' ( i.e as defined by them ).That means Iran, Hizbollah and, perhaps, even Russia who is supposed to be sponsoring the Geneva Peace Conference along with the US.
All Hague has done is give more momentum rather than less to the ratcheting up the violence in Syria and now he has indicated he might be prepared to give weapons to the Syrian insurgents who are trying to scupper the possibility of a negotiated settlement with Assad.
This is what bad diplomacy does. It furthers and deepens the possibility of violence and war.