Guilty as charged

It has been pointed out to me, probably on several occasions, that I should not type two spaces after a period.  I've been doing this since my 10th-grade typing class, so I doubt I can change a 50+-year-old habit.  Today I encountered this rant on the subject (which I typed using two spaces after periods):
The two-spaces-after-a-period construction is outmoded and has no place in modern communication.  It’s not a coincidence that many of my friends who still use two spaces work in finance and law—two decidedly old-school industries populated by people who grew up in the two-space heyday.  The practice should be eradicated for good, especially in the digital communication age, when every device has proportional fonts.  Design experts agree that using two spaces creates an unsightly amount of white space, and increases the chance you’ll have a “river” snake its way through your paragraph.  Worse, it makes a person look old and out of touch.
Here is the same text typed using one space after the periods.
The two-spaces-after-a-period construction is outmoded and has no place in modern communication. It’s not a coincidence that many of my friends who still use two spaces work in finance and law—two decidedly old-school industries populated by people who grew up in the two-space heyday. The practice should be eradicated for good, especially in the digital communication age, when every device has proportional fonts. Design experts agree that using two spaces creates an unsightly amount of white space, and increases the chance you’ll have a “river” snake its way through your paragraph. Worse, it makes a person look old and out of touch.