He is telling them that even this supreme sacrifice, if not motivated by love, accomplishes nothing. Paul is tactful. But he's not being subtle. He wants them to know what he's talking about. So as we continue the reading, bear in mind that when he says something that love is not, you can be sure that the people of Corinth will recognize that as something they have been doing.
Love is patient, love is kind.
It does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil but rejoices with the truth. It always protects, always trusts, always hopes, always perseveres. Love never fails.