Here's the offending paragraph:
This Vatican Council declares that the human person has a right to religious freedom. This freedom means that all men are to be immune from coercion on the part of individuals or of social groups and of any human power, in such wise that no one is to be forced to act in a manner contrary to his own beliefs, whether privately or publicly, whether alone or in association with others, within due limits.
The council further declares that the right to religious freedom has its foundation in the very dignity of the human person as this dignity is known through the revealed word of God and by reason itself.(2) This right of the human person to religious freedom is to be recognized in the constitutional law whereby society is governed and thus it is to become a civil right.
Yes, this is very much the "offending paragraph" - so much so that it's pure heresy. From
Quanta Cura, Pope Pius IX, December 8, 1864:
"For you well know, venerable brethren, that at this time men are found not a few who, applying to civil society the impious and absurd principle of 'naturalism,' as they call it, dare to teach that 'the best constitution of public society and (also) civil progress altogether require that human society be conducted and governed without regard being had to religion any more than if it did not exist; or, at least, without any distinction being made between the true religion and false ones.' And, against the doctrine of Scripture, of the Church, and of the Holy Fathers, they do not hesitate to assert that 'that is the best condition of civil society, in which no duty is recognized, as attached to the civil power, of restraining by enacted penalties, offenders against the Catholic religion,
except so far as public peace may require.' From which totally false idea of social government they do not fear to foster that
erroneous opinion, most fatal in its effects on the Catholic Church and the salvation of souls, called by Our Predecessor, Gregory XVI, an 'insanity,' that 'liberty of conscience and worship is each man's
personal right, which ought to be legally proclaimed and asserted in every rightly constituted society; and that a right resides in the citizens to an absolute liberty, which should be restrained by no authority whether ecclesiastical or civil, whereby they may be able openly and publicly to manifest and declare any of their ideas whatever, either by word of mouth, by the press, or in any other way.'"