That's more a problem with the Tories and Theresa May, who were both already comfortable doing business with terrorist supporters and human rights abusers, so their eagerness in paying the DUP to prop her up shouldn't be a surprise.
I know almost nothing about German politics, but it appears their coalitions are at least done with the major parties - not ones who had less than 1% of the vote - so have a greater chance of being somewhat representative.