Punjab Chief Minister Shahbaz Sharif's remarks at his anti-PPP rally on Friday did cross the boundaries of civilised political discourse, especially in their very personal attack on the president. But it is entirely unclear what torching the PML-N's offices in retaliation will achieve, aside from reflecting badly on the ruling party. There does not seem to be evidence of direct instruction from the PPP, but the fact that these offices were not better protected -- even though the attacks did not occur simultaneously -- raises concerns about potentially deliberate negligence on the part of local law-enforcement. There are also troublesome reports from PML-N supporters about having received threats in advance from PPP workers and about the police failing to register cases.The PML-N has said it will not answer with similar behaviour. But it has urged the Sindh government to take action against those responsible, and the provincial home minister has promised a judicial inquiry. This should be carried out as soon as possible, and it must look into allegations of official negligence. Not doing so will only further intensify the divisive politics that is increasingly at play in the country. As Pakistain moves towards Senate and general elections and political temperatures rise, the violent, antagonistic instinct behind these attacks is exactly what political players need to resist.