Personally I find it hard to have confrontations. My own 'style' would be to simply stop seeking this person out. Given a situation of bumping to them I would not ignore them but rather exchange the required social pleasantries and move on. Should they then enquire about doing something I would simply indicate that this wasn't the time, that doing so would have to wait.

As for social media, such situations are sticky. In most you can unfollow someone without unfriending and blocking them entirely.