What one person thinks they're saying and what other people are actually hearing can be wildly different things. I agree with your point, but the way BF communicated it left the door wide open for anyone, including JL, to hear "Joey Labas isn't very good." He should know better, especially after the situation with Hogan, and just said something like "fans always love the backup QB" and left it at that.
I think it's pretty clear what Brian was saying. He was not slamming Joe at all.
In the linked video clip below, I don't think anyone's jaws dropped when Brian said Joe was the most popular person in the program right now and that he will be until he plays. Brian then said Alex Padilla was also popular for a while...until he played. He said once a player plays it opens the door to criticism.
LINK to that Video Clip, so you can see/hear for yourself:
Iowa offensive coordinator Brian Ferentz says the beauty of competition is working to get better.