I hate to say this as a GT3 driver myself, but I think the fault lies with Lieb.  I have driven Sebring many times and unfortunately the line Lieb took at that speed would force him to track out into the Panoz.  Also the lateral loads on the cars in that turn almost prevent any lifting of the throttle without spinning.  The Panoz really did not have any choice but to hold his line.   I just find it surprising that Lieb pushed so hard to pass at that point with about 2 hours left in the race and a faster car?!?