A mature democracy should be able to handle a diverse range of views, even ones that people might find offensive
Yes this is a lovely high school politics sentiment but it's not what is at play here. There is nuance to politics and social issue. It's not about "handling" or tolerating views one doesn't agree with, the question is, is it right to stand with people in a political and social context who are actively advocating issues you find completely against your own views, in order to further your plight on one specific issue that you do have common views on?
People saying actually no, I would not be okay with that, it's morally corrupt, and the context in which my views exist and who they are shared with is important, are not simply "intolerant". It's not about this nice we should all get along and be listened to idea. Attending these events in solidarity adds to the voice of those organisations.
If you want to add your voice to the chorus of pro life organisations, or anti same sex marriage advocates, then you do you. I will not under any circumstances be joining you.