First it was bitcoin being decried as a "scam currency". Then bitcoiners called litecoin a "pump n dump" alt-chain. Now its BTC and LTC promoters campaigning against Ripple. Quite interesting...
Ripple has been pre-mined and is not decentralized, but in fact controlled by one entity (regardless of what the creators may claim).
There is a huge difference here. Not even a comparison.
Issues of coin distribution and mining versus no mining is a separate concern. From my vantage point, the great majority of LTC belong to Litecoin founders/investors/miners while the great majority of XRP belong to Ripple founders/investors/gateway-partners. There are trade-offs with either distribution scheme, but "coins to miners" is just one scheme (not the defining criteria for decentralization).