"To my understanding, a Beast Comapion could not be stronger than the Master, so I don't think any beast will make any difference when I am on my own," Alex said, showing his stand to not let Ricin go through a procedure that could claim his life or abandon him.
Alex had a conversation with Ricin, who at this point was intelligent enough to understand and make a conscious decision, and even after knowing the danger, he was stubbornly fixated on going with the training process.
Ricin could not speak, but he could share his emotions very clearly because of the bond the two of them shared, and seeing his resolve to go ahead with the procedure even at the threat of death or worse, Alex could not just ignore it and make the cruel desition for him.