I think there are two issues at play here. One that should not concern the club/players/supporters and one that should:
1. Jake's morally suspect behaviour and his relationship with Abby.
"Famous, good looking, wealthy sports star has sex with loads of women". Not exactly a never before seen headline. Jake has conducted himself poorly, and people are free to agree/disagree with his actions, but it's a private matter that he and his family will have to work through. Personally, I don't agree with his behaviour but I think it was unfair of Abby to slay him in the media like she did. Ultimately, this should concern no one but the Stringer/Gilmore families.
2. Jake's relationship with the 17 year old.
This is where the club/players/supporters should be concerned. There are two options: Jake met her on his own time in a non-playing capacity or Jake met her on club time as part of his Western Bulldogs commitments (as seen with the StK school girl situation).
If it is the former, then the club/players/supporters not be concerned provided it was completely consensual and Jake has not broken any laws (there is no suggestion that he did).
If it is the latter, then the club/players/supporters should be very, very, very concerned. The club/players/supporters have right to be outraged and need to make a stand that his actions were/are unacceptable. There is no way Jake can return to the club.
You missed one other angle. Punting. I hope to God it wasn't on footy games.