Even if you're knitting through the back loop, there is a way to purl that straightens these stitches out so that they're not twisted. It's called combination knitting, and it is a perfectly viable way of knitting in some parts of the world and for some people (I use it for row upon row of plain stockinette stitch because, as you say, this method makes my stitches more even). Here's one site that has lots of information on combination knitting: http://anniemodesitt.com/
and there's also a video on Knitting Help about combination knitting, too.
In fact, I recommend you find and watch videos on different kinds of ways to knit. There are many and one may work better for you.
Note that if you like the twisted stitches (for stockinette stitch), then your method isn't wrong. Also, if you decide to stick with the combination method for all projects, you need to know that the increases and decreases are done differently for combination knitting than what is written in the majority of U.S. patterns.
And finally, I have found that using bamboo knitting needles helps make my stitches very even--no matter what method I use.