1. Slavery

First, I want to emphasize that freedom is a very strong theme in the Bible (a) (b). It's frankly not true that the Bible condones slavery. When certain portions of the Bible describe slavery, it was more of a form of indentured servitude than the abomination we tend to think of. For various reasons, people would put themselves into lifelong work contracts. The Mosaic Law has very progressive laws (at the time) for how masters were to treat their servants.

In fact, the Mosaic Law specifically condemns forced slavery, under the penalty of death (c).

The Bible does encourage the forgiveness of debts (d), and in this context, masters releasing their indentured servants from their contracts was considered a part of this. The entire book of Philemon was basically about this.

Anyway, the American abolitionist movement absolutely had Christian underpinnings, as did the British equivalent (read up on Wilberforce). At a minimum, there are many modern and historical black ministers, like Theodore S. Wright and Dr. King, that would disagree with the idea that Bible says slavery is OK. That sort of thing clearly violates both the golden rule and the idea of imago dei.

Finally, black-market slavery is still a concern, especially sexual slavery. I don't see much in the press about this sort of thing, but I haven't been to a church in the last ten years that didn't make fighting it a special focus in its ministry (e).

2. Causing harm with the intention of doing good.

I absolutely think Christians do this. When this happens, they need to listen and be humble enough to ask for forgiveness and change their ways. The greatest two commandments are to love God completely and to love others as we love ourselves (f). If we're not willing to stop harming and start helping people, we're breaking the second most important commandment directly and the first most important commandment through disobedience.

You probably see people (in shallow understanding of scripture, IMO) justify themselves with Bible verses when people are hurt. This is not Biblical. In fact, the harshest things Jesus said were to religious hyprocrites (g). Jesus has been, and still is, extremely counter-cultural. And religion, in the Bible, is all about charity and doing the right thing (h).

Anyway, I see many, many more Christians deciding to sacrifice their time, money, and energy to help people than I see harm. It's hard to put to fine a point on the hypothetical premise, though.

3. ...if your religion keeps you from having real social contacts, I would urge you to change that, it's probably not good for you in the long run.

Yes. I agree. The Bible is fundamentally about relationships, so a Christian faith with no relationships is incomplete at best.

I actually have much better friendships and my relationships with my family are also better now that I take the teaching in the Bible seriously. With salvation and assurance of a meaningful future, I don't have to worry about myself (i) (j), so I can focus on others' needs, whether they're physical, emotional, spiritual, or relational.

I have never seen someone with worse relationships because of their obedience in the Bible. I have seen people oppressed, mocked, and attacked for their faith and insistence on doing what is right. That's what I was talking about. Sorry if that was not clear.

4. ...unlike real people, god does not actually exist, and you cannot expect anything tangible from god if you need help.... Other people will largely honor your loyalty with their support for you, god won't.

It shouldn't shock you that the Bible teaches the opposite.

And it probably won't impress you that I've found the opposite to be true. God has never let me down, but people let me down all the time. I don't hold that against them, though, since they're my brothers and sisters and they're not doing anything I haven't done before in some way. But God is always there. Often not in the way I want or expect, but God isn't a wingman or a genie that He's obligated to follow my mission and fulfill my wishes.

I will say that you are very assured that God doesn't exist, and logically you shouldn't be. There is no way to prove that the God of the Bible does not exist. There is no scientific experiment you could whip up to use matter to prove the immaterial isn't there. I've wrestled with atheism or perhaps deism before, and I've found that it takes a lot of... well, faith... to assume a negative.

(a) https://www.biblegateway.com/passage/?search=Galatians+5%3A1
(b) https://www.biblegateway.com/passage/?search=Galatians+3%3A2...
(c) https://www.biblegateway.com/passage/?search=Exodus+21:16
(d) https://www.biblegateway.com/passage/?search=Matthew+18%3A21...
(e) http://www.newsmax.com/FastFeatures/christians-human-traffic...
(f) https://www.biblegateway.com/passage/?search=Matthew%2022:36...
(g) https://www.biblegateway.com/passage/?search=Matthew+23
(h) https://www.biblegateway.com/passage/?search=James+1%3A27&ve...
(i) https://www.biblegateway.com/passage/?search=Matthew+6%3A25-...
(j) https://www.biblegateway.com/passage/?search=Philippians+1%3...