why would it wreck the fuel as a whole.
It's very similar to lead which was a lubricant and so you got added wear without it.
No it isn't the same, it makes a difference to the fuels performance, dropping engine performance and costing you in fuel economy as it has a lower calorific value. (just ignoring the potential damage right now).
Lead was there as a lubricant, adding ethanol really isn't much different to adding cereal to a pork sausage, it makes the meat go further for the supplier but ultimately leaves you with less pork and less taste. More profit for a lesser product.