This is an important question and I wish I had a good answer, because I can think of at least one occasion where I should've made a scene but was afraid to do so (although mostly for long term consequences rather than short term discomfort). For opsec reasons I won't be too specific, but some strangers came to promote an extremely ghoulish opportunity for a course I was taking, involving a live presentation and a question session. In an ideal world I would've quickly used that question session to publicly ask how the people promoting this event could sleep at night, why they felt comfortable promoting violence to a young and impressionable audience, if they understood their role in the world as oppressors, etc etc (this wasn't military recruitment but along the same vein). I didn't say anything, and I think back to the rage that I was feeling in that exact moment and I honestly really wonder what I would've said if I did commit to starting a scene. For what it's worth, I've started several scenes since that day, and have lost favor with several people over it. I've also met a handful of allies doing it, which has turned me into much more of an optimist because you never expect people to agree with you when you're the guy making a scene over stuff most people see as normal

Maybe the critical thing is to practice a bit of revolutionary (social) suicide. Knowing what we know and believing what we believe is already gonna alienate people. That's something we need to be cognizant of because it's a basic reality of being a politicized and radical individual within a complacent and stagnating society. But to start to turn the engine and turn your belief into material change, you have to accept that it comes with a cost to your own image socially, and it will make people think you're mentally ill for thinking that starving children to death is wrong, or thinking that burning down the Amazon is not an acceptable price to pay for a 2% increase in quarterly earnings for an agrobusiness corporation you've never heard of. Accept that preemptively, but also, assume that lots of people already feel just as uncomfortable with the thing you're starting a scene about, as there are people uncomfortable about the disturbance.