Yes, I fail to see the problem because as a conservative, if I am not shown the harm that is being caused, I tend to like to keep things as they are. If it isn't broke, don't fix it. And if it is working, don't break it. I generally despise iconoclasm, whether done in the name of religious zealotry or humanist zealotry, and I see little reason to give this cross the Confederate Monument treatment.
That is not an unworthy argument. Certainly, there are plenty of things that my tax dollars go to that I do not want funded, and that if I could simply have these Humanists sue on my behalf to make them stop, would certainly satisfy me. But if you are maintaining that this is the principle that you and the Humanists hold: that a minority people within a community who might not want their tax dollars going to particular monuments or institutions should be able to abolish those monuments and institutions from the public space, but only if they are religious? I do not see the harm that is caused by this monument that is not caused by other similar public monuments that people dislike and/or do not support yet take up public land and that their tax dollars may have been paid to maintain.
For example, what if I were a devout pacifist who was deeply morally opposed to any monument honoring fallen soldiers (whether religious or irreligious) being put up and maintained by my tax dollars because I felt that it was glorifying war? Why should my tax dollars go towards paying for that, even if a majority of my fellow citizens wanted one put up? Or in a more pressing case, we in California are paying for a high speed rail this is going to take decades to complete and is going far, far far over-budget. I believe most citizens in California were misled about the nature of this public works project and it will beggar our grandchildren since they will have to pay for it. Can I sue to have the project stopped, even though I am in the minority? Is that a legitimate grievance?