How accurate are these statements about the naming of Safina?

The Muslim historian, Ibn Qayyim al-Jawziyya, has recorded the following > Mahran was renamed (by Muhammad) Safina (i.e. ship). He himself relates his own story. He says, “The apostle of God and his companions went on a trip. When their belongings became too heavy for them to carry, Muhammad told me, ‘Spread your garment.’ They filled it with their belongings, then they put it on me. The apostle of God told me, ‘Carry it for you are a ship.’ Even if I was carrying a load of six or seven donkeys while we were on a journey, anyone who felt weak would throw his clothes or his shield or his sword on me so I would carry that, a heavy load. The prophet told me, ‘You are a ship’” (Ibn Qayyim, pp. 115–116, al Hulya, vol. l, p. 369, quoted from Amad 5:222). I actually got this from an Anti-Islam website (http://www.faithdefenders.com/islam/muhammad_the_racist_prophet.html) , which claim that this shows how "racist" Islam really is. I tried looking more into the context but unfortunately couldn't find any. For those who are familiar with it, how accurate are these quotes?