Lots of "German" people do crime and harm each other as well. Deport all Germans as well?
People are being so ridiculous with how much they generalize so much.
Germans doing crime in Germany is different than letting in almost 2 million migrants and refugees and not expecting this. The very first and primary goal of any elected leader of a country is to protect their own people first and worry about the others next. Otherwise you have failed as a leader. This is what makes a country a country. The day you care more about Non-Germans over Germans is the day you aren't a leader for Germany.
Also you are wrong in your belief that refugees will commit little crime. Historically, no matter what ethnic group it has been, mass waves of migration and demgraphic change have created tons of chaos and upheaval.
What will happen is, once the dust settles of the migration movement. You will have hundreds of thousands or millions of people raised in a largely different culture, many are uneducated or underskilled and will not find work creating a permanent underclass of people. They will live at or below the poverty level. Their isolation will create slums where only they will congregate. Humans have to eat and want to help their family and so if they cannot find stable or good paying work they will steal and commit low level crimes. This has been seen all the time. Take a look at the waves of Italian immigrants to the US. Take a look at after Partition in India and Pakistan what it was like. Beyond this wave of migrants they will have children and their children will have children. They will grow up in these slums. They will struggle between to nationalities and identities. You're seeing a lot of lone wolf attacks from people born and raised here but who grow up hating the new place right? How they become radicalized. This isn't a new phenomena.
If you are Chancellor of Germany, your goal is to protect Germans from risk, that is first and paramount. The fact you don't really understand this is why you are oblivious to the fact ultranationalism and far right governments are propping up all over.