I never though I would be defending Texas legislature online, but...
According to this website, in Noah Webster's 1828 dictionary, liquor is defined as:
"A liquid or fluid substance. [See Liquid.] Liquor is a word of general signification, extending to water, milk, blood, say, juice, &c.; but its most common application is to spirituous fluids, whether distilled or fermented, to decoctions, solutions, tinctures."
If any dictionary can be considered definitive, the Oxford English Dictionary is it. This is from the OED online, definition 3b.
"Liquid for drinking; beverage, drink. Now almost exclusively spec., a drink produced by fermentation or distillation. malt liquor, liquor brewed from malt; ale, beer, porter, etc. spirituous liquor, liquor produced by distillation; spirits. vinous liquor, liquor made from grapes; wine."
I agree that the ale thing is a very odd, if that is the Texas legislature's definition of an ale. But malt liquor seems to be a perfectly valid term that one could, if one wanted, use to refer to any grain-based alcoholic beverage.