It’s obvious by the context.
Other see Jesus in a believer and want to know what guides them — what hope they have that others do not.
At that point, the believer has an opportunity to share the love of Christ.
In that Scripture, Paul is admonishing us to always be ready for that eventuality — not to be always ready to argue with other believers about whose -ism is better.
Would you point out to me the context that, you think, supports your narrow reading of 1 Peter 3:15?