On our last cruise on the Star Princess there were two entrances used but the embarkation was still very awkward and took a very long time. That was my only complaint on the entire cruise.
Regardless of one's political party, I would hope that all passengers would do their best to understand that disabled passengers need to have accommodations made to ensure their comfort and safety. Law suits are costly for cruise lines and injuries are costly to passengers in many ways. It makes sense that passengers with wheelchair accessible cabins could be taken to the purser's desk for the bulk of their check-in after proper I.D. is shown. This might help speed up the regular lines too!