No we shouldn't judge the disposition of someone's soul.

However some confuse calling someone from sin with judgement.

St. James says that correcting a sinner has many spiritual benefits, not only for the sinner, but also for us:

James 5:20: let him know that whoever brings back a sinner from the error of his way will save his soul from death and will cover a multitude of sins.

And whether we want to admit it or not, we are indeed our brother's keeper:

EZEKIEL 3

[18] If, when I say to the wicked, Thou shalt surely die: thou declare it not to him, nor speak to him, that he may be converted from his wicked way, and live: the same wicked man shall die in his iniquity, but I will require his blood at thy hand.

[19] But if thou give warning to the wicked, and he be not converted from his wickedness, and from his evil way: he indeed shall die in his iniquity, but thou hast delivered thy soul.

[20] Moreover if the just man shall turn away from his justice, and shall commit iniquity: I will lay a stumblingblock before him, he shall die, because thou hast not given him warning: he shall die in his sin, and his justices which he hath done, shall not be remembered: but I will require his blood at thy hand.

But if you on your part warn the wicked man to turn from his [evil] way and he does not turn from his [evil] way, he will die in his sin; but you have saved your life. EZ. 33:9

Not to oppose error is to approve it; and not to defend truth is to suppress it; and indeed to neglect to confound evil men, when we can do it, is no less a sin than to encourage them.