Chlorine is bad for the biological life in your soil if you're going organic, other than that, plants don't care and many chemical nutrients actually include chlorine as one of the essential macronutrients plants need. And the chlorine evaporating from the water in your pool isn't gonna make it's way back into your soil...Besides it's a pretty miniscule amount...toxic levels for your plant would most likely be toxic for you as well. I"m not saying your friend is an idiot, but he should be giving out misinformation. Fuck, a lot of people treat the water in their hydro setups with chlorine to keep them clean, and the plants don't care one bit. You're good, have fun growing!