The standard YEC excuse is to reject the dating. They do not deny the existence of fossils - they claim the fossils were formed during the great flood, as (literal) mountains of sediment rapidly buried organisms. They go on to explain that the 'scientists' who see the fossils as millions of years old have their judgment clouded by their rejection of Christ - they cannot accept a young age, because to do so would by to admit their own fallibility and lend support to the bible that they hate.
It's almost a half-decent argument - and if it was being used to condemn one form of dating, it would actually sort-of work. Scientists make mistakes. The problem for YECs is that their chronology is in contradiction with carbon dating, potassium dating, polonium halo dates, light-lag distance dates and minimum dates, lunar helium-3 accumulation rates, extrapolated tectonic movement rates, genetic drift common-ancestor dating calculations, common-ancestor ERVs, stellar evolutionary models, observed supernova expansion clouds, archaeological dating, historical records and dendrochronology. I could accept that scientists in one field might make an error rather than admit that everything they know is wrong, but for scientists in so many different and entirely unrelated fields to all make the same mistake is utterly ridiculous.