You are both right
HR is correct in directing you to steer away from "non work related questions" to an extent although I find it harmless to ask a person what they like to do as long as you steer away from legal areas. Because of the legal ramifications that exist inour current society, your company may have been burned by an inappropriate question asked by a manager. Sure sounds like it if HR is sitting in on an interview; that's unusual.
You can determine soft skills by structuring the question to a work related situation. For example, to determine whether the person is a team player, you can structure a question such as, "How would you describe yourself in the workplace - independent worker, prefer to be part of a team, leader, follower, etc.?"
Ask several open ended questions that allow the candidate to give you more than "yes" or "no" or multiple choice answers you provide. Even in the question above, if the answer is, "I'm a team player.", you can ask the candidate to explain why and give you work related examples that support the answer. Often, the explanation actually points to something else or creates additional questions that you will want to ask.
I wouldn't let the fact that HR is there deter my ability to get underneath the soft skills. It's easy enough to do by asking work related questions. I would certainly try to understand why HR feels there is a need to be in the room. You may find out that you are the one that has burned them in the past and don't realize it. It helps both of you to know why they feel a need to be in every interview.
