They are fighting the charges including the part about lying about it. Giving false statement is mandatory for any of the charges to stick. Remember, they're trying to pin these guys as having punched him and then lying about the incident afterwards. I find it ironic that some already believe they lied.
The SEALs had the option of taking a Captains Mast which would have given them a slap on the wrist but a permanent mark in their profile (records). They are fighting this tooth and nail saying they did nothing of the sort.