According to mainline Protestant Biblical Literalists, there can be no Biblical justification for sinning. Sinning is transgressing against God's law, our Savior died to pay the penalty for our sins, and to continue willingly in sin is completely anti-Biblical.
Hebrews 10:26 (KJV)
For if we sin wilfully after that we have received the knowledge of
the truth, there remaineth no more sacrifice for sins
Absolutely mainline Protestant Biblical Literalists recognize that there's nothing Biblical about sinning and not walking in love. To attempt to justify being unloving would be the same as attempting to justify any other sin. It is, however, reasonable to justify speaking God's Truth even if it offends someone.
The people in question may not think they are ignoring the principles of walking in love. Quite often we do or say things that come out looking and sounding differently than what we mean.
From a mainline Protestant Biblical-Literalist perspective, pointing out sin isn't unloving. Exposing sin is a necessary part of witnessing to the typical evangelical Protestant. It's part and parcel of attempting to save souls. It's included in the Romans Road for a reason. But sometimes it offends people.
- A Preacher preaching on homosexuality may have no hatred at all toward homosexuals, but to the homosexual, it sounds hateful.
- A preacher preaching against alcohol may not hate people that drink, but people that drink might think the message was hateful.
I'm sure the list can go on, but in these cases, a preacher may actually be acting out of love.
In such a situation, it would be perfectly reasonable for the Christian in question to attempt to explain that they didn't mean to be un-loving. It would also be perfectly acceptable for the Christian to stand by God's Word, even if it offends. There are situations where it is simply not possible to stand firm in God's Word without offending someone.
Then there are the times when we really are being unloving. In those cases, it's absolutely against mainline Protestant Biblical Literalist beliefs to attempt to rationalize or justify the behavior. In those cases, we believe we need to repent, ask God to help us to overcome that tendency, ask for forgiveness, and thank God that He forgave/forgives us in spite of the fact that we're not perfect.