Can Logia users be hurt by intangible attacks? After reading chapter 757 I wondered the following:


   Rayleigh explained that objects like your body or other weapons could be imbued with Haki, but what about waves, beams or slashes? After reading the fight between Sabo and admiral Fujitori, it made me wonder if admiral Fujitora would be able to actually hurt Sabo with his power instead of just toying him around. I first thought something similar after seeing Law fight Smoker in Punk Hazard. Law didn't hurt smoker at all, while he sliced up every other person and every object nearby. He had to subdue him by taking his heart and he did so by actually touching him and not by using a long-ranged attack. At first I thought it was because Smoker could block or evade all his slashes, but now I start to think it was because Logia users can't be hit with intangible attacks.
Technically the answer is yes, as any Logia can be hit by any sort of attack if they're in their flesh form, either because they were caught off guard and didn't reflexively transform, or if they wanted to take the hit (for example to shield someone else), or when they are wearing sea stone handcuffs.

I think the answer to the question of whether intangible attacks can hit logia users in general though is no.

Logia users have two ways of evading attacks in general, they can become their element, such as when Crocodlie is hit by bullets and simply becomes sand where the bullets hit and then reforms, or by changing their shape they can avoid the attack, such as when Aokiji opened up a hole in his own chest when Whitebeard stabbed him with a haki infused bisento. 

I think the first method suffices for a basic intangible attack, as from what we have seen it is not possible to use haki on an intangible attack.

Sword beams are different, as they look intangible, but other than with Law, who uses his devil fruit, what swordsmen such as Zoro and Mihawk do is swing their sword fast enough to send the air in front of the sword flying at you at very high speeds, and they can transfer haki to the air itself, as when Zoro sliced Monet.

However, proper intangible energy based attack, such as Enel's Lightning, Kizaru's light and possibly Fujitora's gravity have never been shown to have haki infused in them, and Rayleigh's explanation didn't mention this as a possibility. 

Also, there are relatively few intangible attacks in One Piece as a whole, some which seem to be such as Ace's hiken are in fact Ace turning his fist into fire, making the fire huge and hitting you with it, so this attack could easily contain haki. Ace's move where he fires fire through his fingers like a gun however, probably could not contain haki.

I don't think it is possible, unless you were to hit them when they are in their flesh form, or with their eleme metal weakness, as the only thing that can normally hit a logia's true body when they are transformed is busoshoku haki.