In that passage you are referring to some even said ''I am of Christ''! The problem wasn't Paul, Cephas, Apollos or Christ...the problem Paul was rebuking was the emphasis on 'I' (pronounced as 'eye' or 'ay').
1Co 1:12 Now this I say, that every one of you saith, I am of Paul; and I of Apollos; and I of Cephas; and I of Christ.
1Co 1:13 Is Christ divided? was Paul crucified for you? or were ye baptized in the name of Paul?
Do we not all belong to Christ? Did Paul die for us? Were we baptized in Paul's name? Do we follow Paul or do we follow Christ?
Why the division to follow many, when we are to follow One? Don't follow me or that one, follow Christ.
Later he says to those who would follow another besides Christ that they who they wanted to follow were nothing more than workers in the field.
Why should we follow another in his teachings (his ism) when we have Christ to follow?
P.S. all these questions were rhetorical, no need to answer them.