Twenty years ago when I started basic typography on a computer double spaces especially after a period were also evil. If you look at any professionally designed book, magazine or website it is the same, one space after a period.
Sorry, but I just can't buy into the claim that it was "evil". I started doing typography (nroff, groff and TeX) on computers 30 years ago and to this date I still see nothing "evil", either with 2 spaces. 1 space, or 1-1/2 spaces (granted I distinctly dislike no space). Which I use depends on what the work is supposed to look like. I'm the kind of guy that literally goes over things with a magnifying glass, and might move parens up or down a point or two, commonly moves the dash in a telephone number up or down a point or two, and yes I use different spacing between sentences.
Which is to say that I am extremely critical about the form of work that I produce.
For some reason there seems to be an outbreak of users of this site that think we are in the age of the typewriter.
Please, one space after a period, you are hurting my eyes.
I could care less whether someone else uses two spaces or one after a period. It's a matter of personal style, there is no right or wrong as such. If the boss, or the specified style guide, says this or that, do it. Otherwise, take your pick. Who cares!
And note that almost all style guides will say that 1 space is more common, and 2 spaces is not wrong.