It depends on the person.

People with severe dryness, irritations or allergies to sulfates shouldn't use them. For most, it's strictly a matter of preference. I personally have used them for the better part of 30 years without any problem. My sister has a different hair and skin type, and also colors her hair regularly, and she prefers sulfate-free shampoo. So it varies, obviously. Everyone reacts differently.

As to whether or not they're "bad," you should check your sources. Anytime someone denounces a product or ingredient it is usually from negative personal experiences, which may not be the same experience that you would have.
    Also, salons will often generate negative rumors about ingredients in drugstore brand shampoos so people will buy the expensive salon products instead. They're just trying to make money like everyone else. It's hype.

Your best bet would be to try quality shampoos - one with sulfates, one without - and decide what you like best. HTH