Why doesn't it stand up as an argument though? Just repeating that something is wrong but not saying why isn't an argument either.
Because the facts quoted are not relevant to the argument being made. I do not know how to make it any clearer than that.
Whatever level of debt is acceptable is dictated by market conditions, what the normal level is, what the prospects for the future look like etc. You cannot say "Well it was 100% in 1842, therefore it would be fine at 100% now". One thing does not follow the other.
If you cannot understand that, you're either wilfully misunderstanding, or really shouldn't be allowed out on your own.