Include as an author someone who contributed to financial support only? I am co-authoring a physics manuscript with some students and colleagues. The results in this has been obtained by means of a grant to which multiple people have participated.Because the main research project reported in the grant proved to be too hard, we switched to a backup project, which is the subject of the paper. 

One of the authors just asked me to include as an author one of the persons who contributed to the grant writing, even though this person made no scientific contribution to the paper, because of the subject switch above. 

Is it fair and honest to include this person?

I am asking because if I feel like this is not fair, but if I refuse, this would put me in a difficult situation with the colleague who asked, potentially ruining our future collaborations with him. What should I do?
I think (hope) that most people in academia would consider it improper to include, as an "author", anyone who didn't contribute to the content of the paper. There are some exceptional cases that are questionable, but this one seems pretty clear. 

But the paper might properly include an acknowledgement section naming the person and thanking them for their help in obtaining funding for the project.

But I recommend not degrading the meaning of authorship by naming others. 



Note that some of the exceptions, such as including a PI as an author, are justified, at least in part, because the PI, in addition to funding and running a lab/project also contributes general guidance and conceptual background to the work that goes on there. They have a continuous presence that impacts all the work in the lab. And some consider this to be improper, also. But it is highly variable by field.