Did Bronco get grief about bringing in walk-ons like Andrew Rich and Ziggy and starting them? Of course not, he should be applauded in those instances. Similarly, Sitake should be applauded for Wilgar, Milne, Tanuvasa, etc.
Each of the above guys is a scholarship-level player. Coaches get grief when recruiting is so bad that non-scholarship level walk-ons are starting because of bad recruiting (e.g., Povey, Thorson, etc.). BTW, I even love the non-scholarship level walk-ons that get playing time for BYU. They always play their heart out for BYU. Their failures are in actuality coaching failures IMO (generally, in the form of recruiting).