Peter says, “As each has received a gift, use it to serve one another as good stewards of God’s varied grace. Whoever speaks, as one who speaks oracles of God” (1 Peter 4:10–11). In other words, when we open our mouths to speak for the glory of God, which should be always, there should be a concern to steward our mouths — our tongues — to steward the gift of truth and the gift of grace.
Let it sober us that Christians represent God. We are Christians. We are walking representatives of Christ. We shouldn’t be just slinging around opinions without some sense of sobriety and responsibility for why we hold them and what effects they are going to have and what truth they might encourage or discourage. Therefore, it is different to have a merely personal opinion that is not rooted in God’s Word and to have what I would call a conviction that we believe is deeply and truly rooted in God’s Word.’
Source: John Piper, “How Often Should We Voice Our Views on Homosexuality Online?” (desiringgod).