I personally have trouble understanding why people are so against drafting defensemen high. Ekblad will be the same player whether he's drafted 10th or 1st, so if he's the BPA, you take him. Using a high pick on him will have absolutely no affect on whatever he becomes.
I don't think people are concerned he will become a lesser player if he's drafted early, it's just that defensemen take longer to adapt to the pro game than forwards. They're looking for a more immediate impact, so they want to go with the forward.