is there a reason why the composer liszt only used male voices in the
'chorus mysticus' section of his faust symphony?

Here's one viewpoint:

"Like the 'Gretchen' movement, the 'Chorus Mysticus' can celebrate
woman only by negating her. Liszt's hymn of praise to the eternal
feminine is unmistakably fervid, but it is also specular, in the
manner of the gaze: a thinly disguised celebration of the eternal
masculine.

This internal contradiction appears both expressively, in Liszt's
choice and disposition of vocal resources, and formally, in the
disruption of large-scale harmonic and melodic activity.

The most obvious element of male-centeredness in the 'Chorus Mysticus'
is the fact that the music is for male chorus and solo tenor. In
contrast, the 'Chorus Mysticus' of Goethe's Faust is deliberately left
ungendered at the conclusion of a slowly evolving antiphony of male
and female voices. Goethe's chorus removes sexual difference from the
sphere of persons to the sphere of principles: the eternal feminine is
precisely that which beckons, leads onward, an 'us' that is both male
and female. But the 'us' of Liszt's 'Chorus Mysticus' is explicitly
and exclusively male. The feminine may lead this 'us' to the
fulfillment of "our" energetic striving, but she can do so only as a
rhetorical figure within the discourse of a band of brothers in which
she has no part."

http://content.cdlib.org:8088/xtf/view?docId=ft7j49p1r5&doc.view=content&chunk.id=d0e4395&toc.depth=1&anchor.id=0&brand=ucpress

Perhaps it is not superfluous to translate the German text in the
first lines of the site Pinkfreud posted:
"The finale of Liszt's Faust Symphony is supposed to be a setting of
the "Chorus Mysticus" that concludes Goethe's  Faust . Liszt's
repetitions of the text, however, suggest that the movement is
primarily a setting of just two lines: the famous closing couplet,
"Das ewig Weibliche/Zieht uns hinan."

There are more poetic translations, but a rough one could be:
"The eternal-feminine draws us on."

It is only appropriate for the line to be sung by a men's chorus  - in
the context of Goethe's Faust.