I've been over 40 countries, some for several times and I can't say Yemeni people is less friendly. To me they are more.
I am Muslim and was taking a picture of a cemetery in that area called Hadramaut from outside of the cemetery. It was a men cemetery (it is separate in Yemen). Some people came toward us and said not to take picture of it. We said we are also muslim and we are not inside, though we can.
They resisted and tried to argue and kick. Thanks God we had our driver (of the jeep) very near and he run for help. Nothing happened and if it happens to me sure worse happens to other tourists.,
I can say Yemeni people are poor, brave and very friendly. Most important, they are very sensitive about their nationality and religion.
We can't say Yemeni people are not friendly because of this. Sure they are much better than most European countries when it is about racism and nationality.
"where the traveller goes, nobody knows ! "