I ask because there are some people I don't care to see in heaven ...but the alternative for them is unthinkable.
I think this lesson taught by Jesus addresses how you feel:
Matthew 5
43 “You have heard that it was said, ‘You shall love your neighbor and hate your enemy.’ 44 But I say to you, Love your enemies and pray for those who persecute you, 45 so that you may be sons of your Father who is in heaven. For he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust. 46 For if you love those who love you, what reward do you have? Do not even the tax collectors do the same? 47 And if you greet only your brothers, what more are you doing than others? Do not even the Gentiles do the same? 48 You therefore must be perfect, as your heavenly Father is perfect.
And this from Romans 12:
Marks of the True Christian
9 Let love be genuine. Abhor what is evil; hold fast to what is good. 10 Love one another with brotherly affection. Outdo one another in showing honor. 11 Do not be slothful in zeal, be fervent in spirit, serve the Lord. 12 Rejoice in hope, be patient in tribulation, be constant in prayer. 13 Contribute to the needs of the saints and seek to show hospitality.
14 Bless those who persecute you; bless and do not curse them. 15 Rejoice with those who rejoice, weep with those who weep. 16 Live in harmony with one another. Do not be haughty, but associate with the lowly. Never be wise in your own sight. 17 Repay no one evil for evil, but give thought to do what is honorable in the sight of all. 18 If possible, so far as it depends on you, live peaceably with all. 19 Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, “Vengeance is mine, I will repay, says the Lord.” 20 To the contrary, “if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by so doing you will heap burning coals on his head.” 21 Do not be overcome by evil, but overcome evil with good.
I think once someone understands their own depravity and what God saved them from, it is easier for them as they mature in faith to understand the sins of their enemies. This understanding makes it easier for them to show mercy when mercy is needed. I have a ton of enemies that I can be harsh with, especially when it comes to other professing Christians who deny fundamentals of Christian doctrine or pervert them. I don't like these people, at all. However, were any of them hungry, or needed a place to stay, or needed some money, if I was in a position to help, I would not turn them down. I don't think we have to like someone in order to love them and show them mercy by having compassion on them in their time of need, regardless of how we feel about them otherwise.
As for Christians causing Christians to sin, I dunno. Jesus goes on in Matthew 18 to speak on forgiveness and how to approach a brother or sister who is offending.