I think there is gross exaggeration going on here. Not a single Muslim would say that worshiping graves is acceptable. To suggest that it is somehow linked to Sufism is grossly disingenuous. The issue of building over graves, though, is an issue of Fiqh and there is a difference of opinion on this issue amongst the Shafi'is. Those who should be asked would be the Shafi'is since it is an issue of fiqh of their madhhab. But instead, a leap from building over graves to worshiping graves is being made, which none of the Shafi'is agree with either. Grave worshiping is a side effect of jahiliyyah, not Sufism nor due to ikhtilaaf in a madhhab. People do lots of weird thing without any reason. I've seen people rubbing the Kiswa of the Ka'bah as if to receive barakah from it. I've seen people push and fight to go to the Hajr-al-Aswad (when kissing the Hajr is sunnah, while fighting and pushing to get to it is haraam). All this happens under the sight of the muttawween but it is obvious that both these acts have little to do with Sufism or Salafism, but with jahiliyyah.