Compare Clement's citation of his own gospel in Stromata Book Seven:
"Unless ye hate father and mother, and besides your own life, and unless ye bear the sign." (ἐὰν μὴ μισήσητε τὸν πατέρα καὶ τὴν μητέρα, πρὸς ἔτι δὲ καὶ τὴν ἰδίαν ψυχήν, καὶ ἐὰν μὴ τὸ σημεῖον βαστάσητε)
with the parallel saying which appears in the gospel of some heretical group earlier in Stromata 3:
They quote the words "Anyone who does not hate father or mother, wife or children, cannot be my disciple." (ὃς δ' ἂν μὴ μισήσῃ, φασί, πατέρα ἢ μητέρα ἢ γυναῖκα ἢ τέκνα, ἐμὸς εἶναι μαθητὴς οὐ δύναται)This is not an exhortation to hate your family, since Scripture says, "Honor your father and mother, for it to be well with you."
Two Christian groups neither using a canonical text.
The canonical texts have little or nothing to do with either quote:
Luke 14:26, 27 If anyone comes to me and does not hate father and mother, wife and children, brothers and sisters—yes, even their own life—such a person cannot be my disciple. And whoever does not carry their cross and follow me cannot be my disciple.
εἴ τις ἔρχεται πρός με καὶ οὐ μισεῖ τὸν πατέρα ἑαυτοῦ καὶ τὴν μητέρα καὶ τὴν γυναῖκα καὶ τὰ τέκνα καὶ τοὺς ἀδελφοὺς καὶ τὰς ἀδελφὰς ἔτι τε καὶ τὴν ψυχὴν ἑαυτοῦ, οὐ δύναται εἶναι μου μαθητής. ὅστις οὐ βαστάζει τὸν σταυρὸν ἑαυτοῦ καὶ ἔρχεται ὀπίσω μου, οὐ δύναται εἶναι μου μαθητής.
Matthew 10:37, 38 Anyone who loves their father or mother more than me is not worthy of me; anyone who loves their son or daughter more than me is not worthy of me. Whoever does not take up their cross and follow me is not worthy of me.
ὁ φιλῶν πατέρα ἢ μητέρα ὑπὲρ ἑμὲ οὐκ ἔστιν μου ἄξιος καὶ ὁ φιλῶν υἱὸν ἢ θυγατέρα ὑπὲρ ἐμὲ οὐκ ἔστιν μου ἄξιος· καὶ ὃς οὐ λαμβάνει τὸν σταυρὸν αὐτοῦ καὶ ἀκολουθεῖ ὀπίσω μου, οὐκ ἔστιν μου ἄξιος.
The saying Clement cites from the mouth of his opponents most closely resembles part of Saying 101 of the Gospel of Judas Thomas:
He who has not, like me, detested his father and his mother cannot be my disciple
Stephan Huller has had a life long interest in religion and spirituality 
dating back to conversations with his grandfather, Gaston Frank. "He said we represent one of the last descendants of the Frankist Jewish faith in the world," he muses. "I grew up thinking that our family was something like the Last of the Mohicans."