The Church of Christ, at least where I attend, teaches it preachers to not say “in my opinion” or “I think”. However, these phrases may save a preachers soul. If you say something is the word of God and it isn’t or if you are just plain wrong these phrases could save you from God’s eternal judgement.
If you let the people know your thought isn’t necessarily the word of God you cover yourself and you give them a chance to consider the issue or thought on their own. You give them the opportunity to form their own opinion.
Opinions aren’t bad, but serving up doctrines of men as the word of God could prove deadly both to the preacher and the listeners.