Basically, don't.

Do not repost a craisglist or other classified ad here asking someone here to "please adopt the poor pig" ... Instead, if you want to spend your time helping the pig, contact the person who posted the ad and encourage them to join GuineaPigZone and post the ad for the pig THERE.

Then, walk away or help them privately. There's no need to post about it here or repost the ad - which really usually only encourages members here to spam and harass the person who posted the ad, since the reason for YOU reposting it here is a roundabout commentary on the owner's poor care. There's no reason for that and it generally benefits no one at all, least of all, the pig because when you alienate and basically harass the owner, the more likely outcome is that the owner's going to shut down rather than open their minds and hearts to a barrage of messages about all they're doing wrong, especially when they're looking to offload the animal in the first place.

Please & thank you.