I have seen this "soft tissue was found in T. rex bones, ergo Young Earth Creationism is true!" nonsense thrown around by creationists far too many times. Yet I suspect that absolutely none of them have bothered to look up any of the research that Mary Schweitzer, the person who discovered the fossilized soft tissue they keep on referencing, actually did on the subject.
If they had, they'd know that Schweitzer et al. detail a number of hypotheses which are capable of explaining why the fossilized Tyrannosaurus rex soft tissue they discovered was so well-preserved.* And you know what? Not a single one of those hypotheses set forth by Schweitzer et al. invoked a young earth or any sort of supernatural entity.
In another paper that Schweitzer wrote on her discovery, she and her co-authors compare collagen taken from the T. rex fossil with the collagen found in a number of modern organisms, including a newt, a mouse, a fish, a chicken, and a frog. Do you know which of these organisms the sequences T. rex collagen they were able to recover most resembled? The chicken.** Schweitzer's discovery is yet another that the closest living relatives of the dinosaurs are birds. The fossilized T. rex soft tissue has led to the discovery of another piece of evidence indicating that birds evolved from dinosaurs. And yet creationists like DJ keep on citing the fossilized soft tissue that Schweitzer discovered as if it were evidence against evolution.
*Schweitzer MH, Wittmeyer JL, Horner JR. "Soft tissue and cellular preservation in vertebrate skeletal elements from the Cretaceous to the present." Proceedings of the Royal Society B - Biological Sciences. Vol. 274, Issue 1607 (2007): 280 - 285.
** Asara JM, Schweitzer MH, Freimark JM, Phillips M, Cantley LC. "Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry." Science. Vol. 316, Issue 5822 (2007):183197.