While saying the word “lady” in any context and in any time period is nothing short of disgusting, there is a distinct brand of dicklessness to the “man” who actually types the words “Hey lady” out into a text. It shows that the “man” was given greater opportunity to truly consider what words he was using to address not a lady, but a girl, woman or female. When a “man” uses the word “lady,” it simply conjures the lyrics to “Dude (Looks Like A Lady).”
Of all things a “man” can text (especially in the middle of the night), it seems that “Hey lady” is by far the most condescending and hackneyed. In general, you will be lucky if any self-respecting woman responds to your banal greeting. And if she does, then, indeed, you deserve one another.