Great points. I can see the record argument, but that too seems unconvincing given how much our understanding of training has improved over time. Are we going to limit ourselves to training regimens developed decades ago in the name of fairness? I think the vast majority of people would see that as silly.

Another argument against records: You'll still have records set by people who use performance enhancing drugs, but you won't be able to prove it solidly. For example, the women's 400 meter run record was set back in 1985 by Marita Koch. Very few women have come close to her time, suggesting she probably did performance enhancing drugs, and there's documentation suggesting that she did. Yet the record still stands.