Though I do not think as Christians we should ever be mean and hateful towards anyone, we are given commands from Scripture about how to treat the unbeliever. First of all, we should do all things to the glory of God, whether in word or deed. We should also be ready always to give an answer to anyone who asks us, in gentleness and with respect. However, we must come out from the ungodly world system and be separate. We are told in Ephesians 5:11-12:
And have no fellowship with the unfruitful works of darkness, but rather reprove them. For it is a shame even to speak of those things which are done of them in secret.
We must also do as Timothy was exhorted in II Timothy 4:1-4:
In the presence of God and of Christ Jesus, who will judge the living and the dead, and in view of his appearing and his kingdom, I give you this charge: Preach the Word; be prepared in season and out of season; correct, rebuke and encouragewith great patience and careful instruction. For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths.
We should always treat others with respect because we do not ever know how God is working in their hearts, but we should NEVER shy away from rebuking and reproving false teachings. Also, we should know when to walk away from those who refuse to hear the Gospel after many attempts. There are many, sadly, who will go to their graves hating the very idea of God. We would do well to note them and pray for their repentance, but we should avoid "foolish and unlearned questions", "profane and vain babblings, and oppositions of science falsely so called" and "foolish controversies and genealogies and arguments and quarrels about the law, because these are unprofitable and useless". All wise and helpful advice, I think.
Yet many are just attacking and insulting the folks -- like I gave the example of the Born-Again behavior in South Canara -- it set back not only the BA's spreading of the Word, but set back that of the Church's momentarily.
"rebuking and reproving false teachings." is not the same as insulting a person or his (non)beliefs as traitorous or worse.