I hear Christian's say this all the time, especially on this forum, yet I don't know what the biblical basis is for it.
I Cor 13
4 Love is patient, love is kind. It does not envy, it does not boast, it is not proud.
5 It does not dishonor others, it is not self-seeking, it is not easily angered, it keeps no record of wrongs.
6 Love does not delight in evil but rejoices with the truth.
7 It always protects, always trusts, always hopes, always perseveres.
8 Love never fails.
Rejoicing with the truth is different than beating someone ove the head, senseless with it.
Christians use "speaking truth is love" to defend when their words come across as judgemental, hurtful and hateful.
If Christian's learned how to express love in a manner that can actually be received by sinners as being thoughful and caring, rather than coming across as judgemental and hurtful, it would open the doors to be able to speak truth in manner that is truly preceived as love by those who don't know God.
This is not just a theory, but something I have real word practical experience with, so please don't tell me it won't work. It's pretty obvious"the speaking truth in love" has won very few sinners to Christ.