Here's the article where the 25-1 reference originates. If you actually read the article, you'll see this sentence:

"In the first intifada, which erupted in 1987 when Arafat was still away from the land, the ratio had been 25 to 1."

In the same paragraph, you'll find the following:

"The logic behind Arafat's ruthless method is easily seen. In the cold calculus, the balance of casualties now runs 3 to 1–in 18 months, 1,200 Palestinians have been killed for 370 Israelis."

So, back in 1987 when they had kids throwing rocks at soldiers, 25 Palestineans were killed for every Israeli. Now with suicide bombers, snipers, etc., there are 3 Palestinean deaths for every Israeli death. That's an 8 fold improvement in the kill ratio.

Anyone who actively shoots or bombs troops is a combatant, not a civilian. Combatants are legitimate targets on any battlefield. There isn't a soldier in any army who is going to say, "Well, he's shooting at me but I can't shoot back because he isn't wearing a uniform."