No, that is not true. XRP is a crypto currency, and you need an account's secret crypto key to do anything with the XRP held by that account. The validator network validates the cryptographic signatures on transactions and only accepts those that are properly signed with the correct keys.
What about this?
https://wiki.ripple.com/FreezeI wouldn't say you own XRP's if someone else can freeze them..
You did not read that page closely.
XRP cannot be frozen, only IOUs from gateways that have not explicitly disclaimed the ability to freeze individual accounts.
XRP is always safe from freezing, but if you are worried about having your gateway issued assets frozen, you can also choose to only accept IOUs from gateways that have permanently and irrevocably renounced the ability to freeze individual holders of their IOUs.
Do you have a libertarian viewpoint?
Do you believe in choice and free markets?
Then you should have no problems in allowing gateways the ability to either choose to allow freezing of individual trust lines or to disclaim that ability so that they cannot do so.
This empowers the users to choose the gateways that serve their needs, and the added abilities allow gateways to serve the ripple ecosystem who would be unable to do so otherwise.
In either case, XRP cannot be frozen, only gateway assets and only if the user
chooses to hold then. Several gateways have already permanently disclaimed the ability to freeze the assets that they issue. People have choice - The market will decide.