If you search for that website on this forum & at the Better Business Bureau, you might find that you'd like to go somewhere else with your business. Also, almost all reputable fragrance oil supplier's fragrance oils are undiluted, so with that statement, it sounds like they're just trying to scare people.
For fragrance oils I recommend:
Brambleberry
Nature's Garden Candles
Bitter Creek North
Scent-Works
Wholesale Supplies Plus
If you're looking for specific fragrances, you can check
http://www.fragranceoilfinder.com or if you're looking for a supplier in your area, you can check out
http://www.suppliersbystate.com