Earlier today I went out with some non-Catholic friends and the issue of the recent Supreme Court Case legalizing Gay Marriage came up. While I have made clear to these friends before that I agree with the Church’s view of Marriage religiously and do not oppose legalizing gay marriage if it challenges this, I did say that I saw a lot of good in the Case, in part because I viewed civil and Sacramental marriage as separate issues. However, I read online after I got home that such a view is actually heresy and that the document Considerations Regarding Proposals to Give Legal Recognition to Unions between Homosexual Persons conemns my original view. I am willing to admit this, but I am frightened that I, unknowingly, committed heresy or at least grave scandal and may not be able to receive the Eucharist. Did I commit heresy or scandal and do I suffer the consequences of such, or am I OK because I didn’t know better and changed my view after learning?
No, you did not commit heresy. Heresy is the obstinate denial of some truth of the faith. You did not know the Church’s teaching, and when you found out the truth you were open to being corrected. There was no sin on your part whatsoever. In fact, I wish more Catholics had your attitude.
I don’t think you have to worry about the sin of scandal either. It’s true you may have given them incorrect information, but your intention was not to lead them astray. You were just explaining things as you understood it. Perhaps next time the topic comes up you can explain to them what you learned.
But as far as any sin goes, you are fine. You certainly don’t have to refrain from the Eucharist because of it.
The short answer is no, you did not commit any grave sin. You did state a serious error, as you discovered later. We all should be aware of how secularist thinking pervades our society and how we should on guard against it.