The issues not that they are exceptions, but that they exist at all. Mild genetic (birth) defects such as near-sightedness are extremely common. If we are meant to see, why are so many of us born with the defect?
We need teeth to eat, and yet our teeth are poorly designed and rot easily. Why?
Oddly enough... I am not a proponent of ID... but your argument against it is in my opinion weak. Birth defects happen for a number of known and unknown reasons. Sometimes it is just bad luck. My car was created via intelligent design yet... some of the ones built have defects in the manufacturing. It wasn't the designer's fault, it was poor manufacturing (maybe because it was simply a Monday morning...).Point is this doesn't really provide a good argument.
As for teeth and why do they rot... why do they fail at all? Perhaps it is "Planned Obsolescence". I am of course joking... sort of. Our decay and eventual death creates life to exist for others correct? A proponent of ID would argue that death is part of the life cycle that something also designed. In other words, it is all part of the intelligent design.
I think your arguments are not very strong and one could easily use them against you. My suggestion is if you want to fight Intelligent Design... tell the proponents that there are many versions of Intelligent Design and that all of them will be discussed... not just one version. Take the Scientologists and their ideas about "Xenu" and the body Thetans (if you do not know what I am talking about... look it up, basically it is an aliens souls invade our body type of thing).
Another way to fight it is to ask the question,"Is it science?".
I am against the whole idea because this could open up a pandora's box of all sorts of kooks wanting to teach ID about all sorts of things. Plus if I want my children to learn this, I will take them to church. It royally irks me and I don't like it one bit.