Use of convicted as a close synonym of convinced or opinionated is rare, but certainly not unknown. For example, in
The Gondoliers, as Grand Inquisitioner Don Alhambra del Bolero tries to overcome objections of Marco and Giuseppe Palmieri against one of them being King, the term is used in this sense, among others:
GIU. Such a king would be a blessing to his people, and if I were a king, that is the sort of king I would be.
MAR. And so would I!
DON AL. Come, I'm glad to find your objections are not insuperable.
GIU. Oh, they're not insuperable.
TESSA No, they're not insuperable.
GIU. Besides, we are open to conviction.
GIA. Yes; they are open to conviction.
TESS. Oh! they've often been convicted.
Here's an example of use in a contemporary blog:
i think that most of you know by now that i am a person with strong convictions but as i get older and hopefully wiser, i am learning that i have often been convicted about the wrong things.