Interestingly, the Motorcycle Safety Foundation (MSF) and every Experienced Rider Course (ERC) I've ever attended places a great deal of emphasis on using the front brake. Additionally, there is an article on this exact topic in the latest edition of Iron Butt magazine. If you take into consideration the weight shift to the front during braking, you'll realize that the rear brake becomes less effective. Dropping the bike in the situation you describe is completely due to the wheel being turned.
If you look at the extreme example of a sport bike doing a "stoppie", they're using the front brake so hard that the rear lifts off the ground. Yet, they do not drop the bike because the front wheel is kept straight.
While it may be true that using the back brake will prevent this issue, it is a bad habit to get into relying on the back brake. There are certainly times when the back brake is needed, such as slow speed manuevering in combination with using the clutch friction zone.
Given my small number of posts on this forum and that I'm going against the majority of posts, I'm standing by for flames. However, as a side note... I have been riding for over 40 years... well in excess of 1 million road miles... and as part of the Navy's requirement, I participate in an ERC every 2 years. Just saying... not a rookie.