Bitcoin, Litecoin, Feathercoin, etc. are all decentralized currencies, and this fact should give you at least one very good reason to trust them.

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.

The main thing which makes bitcoin decentralized is that there's no central authority which can seize your coins. Its the same with Ripple, XRP at a ripple address cannot be seized or moved (without the private key for that address).

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).

That's not information worth noticing, because facts aren't relative. One could easily be a scam, justifying such a campaign.