Yes it is perfectly fine to use auto. As a Professional Photographer I have many tools in my arsenal that I use to do my job. Auto is one of those tools. After all it is on your camera for a reason. A Tool To be used when it's needed.
We were covering a wedding and the weather literally changed constantly. We had from rainy to bright sunny and back again. Weddings are fast paced and the last thing we needed was to blow out these shots if we didn't change the settings for each lighting change. I am a professional and my camera is a professional camera. However I am the crafter and these are my tools.