I support the march's demand but not the organization leading it

A march is being organized in my city around a policy demand I strongly support. I had planned to attend until I read more about the lead organization. It takes several positions on unrelated issues that I do not share, and one of its spokespeople uses language I would not defend.

Friends have divided into familiar camps. One says attendance means endorsing the coalition, because crowd size becomes power for the organizers. Another says refusing to attend over unrelated disagreements is how broad public action becomes impossible. Both arguments have force. A march is not a private thought. My presence contributes to the event's image even if nobody knows my reasons. It also does not follow that every person in a crowd has adopted an organization's entire platform.

I looked for practical distinctions. Is the event centered on one clear demand or branded as a general show of support for the organization? Are speakers announced in advance? Can participants bring their own signs? Is there a conduct policy? Are partner groups named? What will organizers claim afterward about who attended and why?

One option is to join a separate contingent whose sign states the specific demand and whose members have agreed boundaries. Another is to support the policy through a different action: testimony, a local group, or a donation to an organization I trust. Staying home is not the only alternative to joining uncritically.

I do not expect moral purity from every coalition. I do want to know which compromises broaden action and which lend legitimacy to positions I would otherwise oppose.

How do you decide whether to participate in a single-issue event led by a group you distrust on other matters? What would make your support specific enough to avoid a false blanket endorsement?