Even if blood was found as falsely described there is too much other evidence for a very old earth. One would be taking the less unlikely course to try to explain the blood preservation over a long period of time. However, that is almost as unlikely as a young earth.
The lesson for your co-worker to take from this (and many, many other things like it) is that the sources they have listened to are dishonest or ignorant or foolish. The whole YEC camp is rife with those who have a disregard for accuracy.
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