Masud: I have a difficult time of comparing photo's for identifying plants but I suggested a possible ID of Opuntia monacantha earlier, either on this thread or the other one where the photo was posted. Glad to hear that someone familiar with cactus has identified it. It's such a beautiful specimen and your great photo's will certainly add a lot to the database!
I don't think I'd say the "experts" on DG are any better, maybe there is just someone over there who is more familiar with the Cacti family? As to your second question regarding why some on Dg love to rub the fur of the cat the wrong way ...
I never could figure that one out! I don't have a subscription over there anymore and don't miss any of the malcontent that went on over there.