The only time you should be worried about a charger harming a device is if it's rated for a much higher amperage than your device was designed for. Fortunately, the LG G2 can handle up to 2 amps, so it'll charge just fine on pretty much every charger out there, including tablet chargers.
However, like mrsmumbles mentioned, a lower amperage charger will take longer to charge the G2. I would definitely recommend picking up a 1.8 - 2.0 amp charger for your G2 to take advantage of its rapid charging feature.