The dangerous precedent I was referring to is that if Fox gets to erase canon then it will ultimately abuse this power, just look at LucasFilm. A few years ago, it was dictated that the movies were canon 1 and any Clone Wars TV show (microseries and main series) would be canon 2, now that has been completely altered with the microseries being cast out. The Force Unleashed was also a very popular storyline and many fans consider it canon (though some choose to ignore TFU2), now there are talks to throw that story out as well. In all likelihood, what with the new Star Wars trilogy and the multiple standalone films SW fans are promised in the coming years, it is quite likely that the award-winning Clone Wars series, which is considered among the highest canon pier, will be nullified and replaced for future titles as well (just like its predecessors).
If AVP fans give Fox the same power to nullify canon, then the exact same disaster will occur in this franchise as well. In their desperation to maintain a single canon (one that is affiliated with popular views), fans are not realizing the doom they are guiding this beloved series to; can you imagine a world where Fox allows the newest film/game to be canon, then a few years later nullify that title for the next newest title, and then a few years later nullify the new title for the next newest title? At some point, Fox will realize that it doesn't need fans to act as the middleman anymore and can simply nullify canon at will (as LucasFilm is now doing), this calamity has already occurred before and we can't let it take this franchise as well; as a fan of this franchise, you can't tell me you don't view this sort of careless behavior toward the canon of a beloved series to be some sort of moral crime against it (if not a legal one).