Context: Horace is taking a position “above the fray” in commenting on the vices and peculiarities of his nation. Here he imagines the Roman people questioning him:
70 Quod si me populus Romanus forte roget, cur
71 non ut porticibus sic iudiciis fruar isdem,
72 nec sequar aut fugiam quae diligit ipse vel odit,
73 olim quod volpes aegroto cauta leoni
74 respondit, referam. . . .
Translation: But if by chance the Roman people should ask me, why
I’m not pleased with them both, with [ut ]their judgments, as with [sic] their colonnades
and why I don’t chase or flee what [respectively] they like or what they hate,
the [legendary] reply of the careful fox to the sick lion
I give in [my] answer [to them]. . . .
71 isdem, read iisdem, ablative plural, the ablative complement of fruar. I translated this as “with them both”.
71 ut . . . sic: these present a contrast, “just as on the one hand . . . in the same way on the other”
71 “porticibus . . . iudiciis . . . isdem”: ablative complements of fruar.
Once that reading seemed clear, it was easier to catch the contrast presented in the next line.