I have been reading the book of Sirach, which I consider to be inspired, but I've been reading some passages in there that talk about not welcoming in strangers in your house because they might ruin your reputation. How does this square with Jesus teaching about welcoming the stranger in to your house?
My view of the apocrapha is that they are good books to read, but not inspired. They are like books you might pick up at a Christian bookstore-- good to read, but they aren't doctrinally perfect. I do recommend reading them-- my personal favorites are Sirach and Tobit and the extra stories of Daniel-- but we need to recognize that they will contain some errors.
As far as the passages you mentioned in Sirach, you are right that they do seem to contradict the New Testament teaching about hospitality. Sirach is reflecting the fact that hospitality is primarily for those we count as friends, companions, bosom buddies. The Old Testament, especially in wisdom literature (Psalms, Proverbs, etc), emphasize that who you hang with will, to a certain degree, determine your reputation and character. And we know this to be true, to a certain degree-- our friends convince us of our morality. Peer pressure isn't just an issue for teenagers, it is a way of life for all of us.
But in the New Testament, our character is determined primarily by the Spirit. This gives us the freedom to do some things that the saints without the Spirit could not. We are able to love those who, without the Spirit, could drag us down the path of evil. The other thing, is that Jesus is encouraging us to practice benevolence, not only to our friends, but also to those we don't like, even to our enemies, who do evil to us. This takes hospitality to a different level, one in which peer pressure doesn't enter.
Jesus calls us to a higher morality than Sirach, just like the Old Testament. Not a different morality, just to a higher level. Love for others must overcome our personal concern for reputation.