If you see someone who has their Foil, Epee, or Sabre up in the air and carelessly walking around, it's better to NOT fence them. They are what are known as dangerous fencers and don't care about their opponent. They only care about winning and they play dirty.
All these swords, even though they don't have a sharp tip, are still weapons and they hurt.
Before deciding to Fence someone, watch their bouts with other fencers to see how they hold up. Are they aggressive? Too aggressive? These are things to keep in mind when looking for people to share a match with.
Very aggressive Fencers can be dangerous. They tend to strike harder than they should and get frustrated easily when they can't make a touch. This makes them strike even harder. Half the time they probably don't know what it is that they are doing. So, it's better to keep away from them.