Unless things changed this year, which I can find no evidence on www.academyadmissions.com, the Writing Portion of the ACT is not required for USAFA. Other SA and colleges do require it though.
Totally up to the applicant. USAFA doesn't use it to evaluate the candidate currently. Will that change? Maybe in the future but it'd be well publicized ahead of time.
What if my writing score was not that great. (6) would it benefit me to include it or not include it? I know I can re take it for a better score. I am just wondering in case I got another 6.