But “other penalties” need not necessarily equate to coercion. That is my point. The language does not point to it. If you are able to show that in actual fact that “other penalties” are indeed coercive, you may have a point.
Many, many of these canons end up with this anathema warning. Why is this canon in particular falls under the coercive category and not the others? I failed to see the point others are trying to make of this canon.
There are Catholics whose views are not aligned perfectly with the Church, but there is no coercive force to compel them to be obedient. The Church may withheld certain sacraments from those disobedient and to those of extreme disobedience, excommunication.
Secondly, and more importantly this canon according to those who pointed out, applies to those who say it is ok to let those who wanna out , stay out. The Church says it is not ok. If one insist on saying that, the Church says one may be excommed.
If any one saith, (that those who have been thus baptized when children, are, when they have grown up, to be asked whether they will ratify what their sponsors promised in their names when they were baptized; and that, in case they answer that they will not, they are to be left to their own will; and are not to be compelled meanwhile to a Christian life by any other penalty, save that they be excluded from the participation of the Eucharist, and of the other sacraments, until they repent

let him be anathema."
The words that are bracketed in red being what was being said by the offender. This canon provides for anathema for saying those words, it does not provide “other penalties”. The “other penalties” that you mentioned are actually the words said by the offender.
This canon does not address those who doesn’t want to keep their infant baptismal vows anymore.
But this canon does address what is not permissible. The Church didn’t want such people to make statements which may be construed as doctrines/practices by those less knowledgeable for the Church whereas they are not permitted to do so. I can imagine these smart alec offenders telling others that it is ok to do this, ok to do that and not that when they have no such knowledge or authority to advise others on what is permissible or not. That is all I can read from the text. There is no smoking gun. All you have is a mole hill. The Church is wisely prohibiting people from coming out with their own versions of permissible behavior. She has shown leadership in other areas prohibiting wrong interpretations, wrong beliefs, wrong books to read and so on.