Wolf, I entirely disagree with you.
Just like lack of moisture or overuse of certain products (like formaldehyde) can cause your nail to crack, split and peel, using hair products that have harmful ingredients will damage your hair. Using a hair product with a large percentage of alcohol, for instance, will dry the hair shaft and make it more prone to breakage. You are right that both hair and nails are dead cells, but these dead cells still react in certain ways to the chemicals and products that we use on them. We can experience breakage, discoloration and extreme dryness, up to the destruction of the hair itself. You are correct that in all probability none of this is going to cause baldness, but excessive usage of products with certain ingredients can harm the scalp if it comes in contact with it over a long period of time.
Conclusion - skip the hair products with alcohol.