Im going to make this short and sweet. Most of you probably already know what im blabbin about. Diet sodas has a chemical in it called Aspartame.

Aspartame : low-calorie sweetener that is used in more than 5,000 products worldwide

Aspartame causes several different kinds of diseases,
convulsions
dizziness
tremors
migraines and severe headaches (Trigger or Cause From Chronic Intake)
memory loss (common toxicity effects)
slurring of speech
confusion
numbness or tingling of extremities
chronic fatigue
depression
insomnia
irritability
panic attacks (common aspartame toxicity reaction)
marked personality changes
phobias
rapid heart beat, tachycardia (another frequent reaction)
asthma
chest pains
hypertension (high blood pressure)
nausea or vomitting
diarrhea
abdominal pain
swallowing pain
itching
hives / urticaria
other allergic reactions
blood sugar control problems (e.g., hypoglycemia or hyperglycemia)
menstrual cramps and other menstraul problems or changes
impotency and sexual problems
food cravings
weight gain
hair loss / baldness or thinning of hair
burning urination & other urination problems
excessive thirst or excessive hunger
bloating, edema (fluid retention)
infection susceptibility
joint pain
brain cancer (Pre-approval studies in animals)
death

While I agree that aspartame is probably not the best from what I've read there is no research that all agrees on this subject. Can you state your background?

Do you also know that the amount of aspartame that caused cancer in lab rats is the same amount in 5000 bottles of diet coke?

the aspartame isn't the problem, it the phosphoric acid in diet soda that does the most damage.

Here's why: blood chemistry in the body is crucial. when you take in a lot of phosphorus, the body has to have a proper level of calcium to balance it out.
The body will absolutely strip calcium from teeth and bones to maintain blood calcium levels. If blood calcium levels aren't maintained, the heart starts beating irratically, and will eventually stop - cardiac arrest.

So obviously this is why the body is designed to do whatever it takes to keep the blood chemistry correct. So, its not so much the sugar in soda that rots your teeth, as it is the phosphorus.