ἄλλοι δὲ δοκοῦντες φαυλότεροι ἐπιεικέστεροι εἶναι ἄνδρες πρὸς τὸ φρονίμως ἔχειν.
Is the infinitive in the underlined part an accusative articular infinitive (written w/o the article usually),
acc. of respect to ἐπιεικέστεροι?
Yep 
Just to add, I believe the article is mandatory when the infinitive is governed by a preposition, even in the accusative case. Is that right?
Yes. I think you are right, modus. I thought I read it as ἐπιεικέστεροι εἶναι ἄνδρες (τὸ) ἔχειν τὸ φρονίμως.
But i sometimes don’t see very well. How would you read the sentence as it’s written?
My commentary says that it is like ἔχει οὑτωσί, that is the case here, and that πρός = in reference to (LSJ C.III.3.)
Perhaps that Socrates have found them suitable “in reference to being in one’s right mind”.
Yes, or equivalently “with respect to being…”. The πρός here is sort of like a marker of the accusative of respect, I’d say.