If it was on the internet, "camping" most likely refers to the practice of staying hidden in the same spot playing first-person shooters, which makes it easier to kill people but harder to complete team-based objectives.
Campers often camp in such a manner as to gain as many unfair advantages as they can in a fight, sometimes even using glitches or exploits. Everyone hates them because they don't help their team and are incredibly frustrating and repetitive to play against. Campers will never make the first move, so you have to fight them in an area they have carefully chosen.
More loosely, "camping" might refer to any practice that involves waiting in one spot for something. For example... When I played "battlefield 1942" I was famous for camping on the runway to catch the planes as they respawned. I was also famous for "air-camping" the enemy's airport, slaughtering anyone who ventured out into the open or got into a plane.
When confronted with a camper, online etiquette dictates that you demand to know where their "coleman stove" and "tent" and "therma-rest" are.
The compound insult "camping Jew" most likely carries all the meaning of "fucking camper" with the added connotations of the word Jew- that is, a greedy, covetous individual who will perhaps try to "Jew" you out of your hard-earned material possessions.