People shouldn't look down on HR, however they often present themselves as the friendly, impartial intermediaries between employees and the company when they aren't. You should approach talking to them the way you would talking to the police: don't if you can avoid it, but otherwise, assume anything you say can and will be used against you if it's in the company's best interests to do so.
And also less likely to leave but why is that a problem?
In the end all employees are only there to make the company money. I really don't see why HR is any better or worse than the engineering department. Everyone is just trying to make a living so I don't see any point in looking down on them for it.