Faithful Catholics are not permitted to disagree with the documents of an ecumenical council. That's just a plain fact. However, it should be noted that there are many misconceptions about Vatican 2.
Vatican 2 did not give the faithful the right to receive communion in the hand.
Vatican 2 did not say that Mass should be said in the vernacular, in fact it said that Latin should be preserved in the rites and that Gregorian chant should have pride of place in the liturgy. Sacrosanctum Concilium
Vatican 2 did not codify the rubrics of the Novus Ordo.
These are probably the three biggest issues traditionalists take with "Vatican 2," and Vatican 2 did none of these things. Traditionalists who "disagree with Vatican 2" on these or similar grounds are simply confused. They are not actually disagreeing with Vatican 2. They should be encouraged to actually read the V2 documents and understand them so that they can come to realize that Vatican 2 did not call for the innovations which they (rightly) despise in the (common, and illicit celebrations of the) Novus Ordo.
Those who actually object to the teachings of Vatican 2 are heretics.
That being said, Catholics are permitted to object to matters of prudence as they relate to the conduction of the council. For example, allowing Protestant ministers to sit in and have their voices heard in the council seems imprudent, for, while the Holy Spirit will protect the council from error, it is fully possible that the authors of the council documents will be given to choosing vague language that does not clearly contradict Protestant viewpoints, especially if those authors are biased in favor of Protestant doctrine.