Correct me if I'm wrong, but I think the post was meant to describe unfaithfulness in terms of sexual activity with another person - not just giving someone a Christmas kiss, etc.
The things you've given as examples could be classed as annoying to some folk, but hardly stuff that you'd divorce someone for. Going to a strip club isn't particularly offensive. Most sensible wives & gfs'd laugh about it. Not disclosing a teatime meeting could be suspicious - if only for the fact that if it was all above-board, you'd tell your partner about it, and why. The slow dance & Valentine cards are nothing either, providing you do it openly or tell your partner what you're going to do. It's all about trust, but if you have a sexual fling with another person, you're breaking that trust by doing something that should be saved for the one you love, since it's such an intimate act.