Well, when you take the phrase "intrinsically negative" literally its obviously tautologically false.

But what I mean is more like the following. Human beings aren't just detached rational creatures. In fact, we are strange embodied minds for which "happiness," if it is to be sustained at all, requires a variety of stimuli arranged in an appropriate way. Some of that stimuli is unpleasant: being rejected by a partner, failing a test, not being fast enough to win a race, whatever. But separated from all negative feedback the systems which maintain us in something like emotional homeostasis often seem to break down.

There is nothing deep here and philosophers have talked about this one way or another forever: seeking only pleasure and avoiding all non-pleasurable stimuli ends up being bad for us. Of course, that means those unpleasant stimuli are not "intrinsically bad," since they appear to be good for us. Maybe a better way to say it would have been "intrinsically unpleasant."