The phrase "being of opinion" can be reworded in a variety of ways depending on the context and tone of the statement. Some options include "holding the belief," "thinking," "believing," "having the view," "assuming," "presuming," "surmising," "judging," "estimating," "concluding," "supposing," "asserting," "maintaining," "contending," and "arguing." Each of these synonyms can add a slightly different nuance to the expression, emphasizing different aspects of the speaker's confidence or attitude towards their perspective. When choosing a synonym for "being of opinion," it's important to consider the context and how the alternative phrasing may impact the overall meaning and impact of the statement.