I think Shiro looked severely uncomfortable through all of s4 e4. Like more than any of the others. His face when Coran is telling him to (more or less) expose himself to a huge crowd really hurts. Do you think he's reminded of being a gladiator by all this performing?
I don’t think it necessarily reminds him of being a gladiator as much as I think that…
Shiro is a very charismatic person, but his charisma comes from a core of earnest sincerity and heartfelt passion. Also, most of what he talks about is rooted in a personal, powerful sense of both honor and compassion. A term I think of a lot with Shiro’s character is “noblesse oblige”. There’s a certain thematic sense of “royalty” around the role of the Black Lion, and Shiro embodies those virtues in a sense that gives him a kind of Arthurian Hero-King vibe.
In short, Shiro, his ideals, and his compassion for other people are inseparable. These are the integral elements to why he’s doing any of this.
Worm-controlled Coran proposes an incredibly shallow view of Shiro showing off his body and using his looks to charm people and basically advertise a false, constructed persona. Not only is that uncomfortable because Shiro himself is someone who is very particular about how he’s viewed (he takes making a good impression very seriously, shown as early as s1e5) and someone who’s used to being on a pedestal in not always the most comfortable sense…
Shiro has a very high standard of what it means to be a figure people look to. Look at his interacting with Lubos in s2e4. In Shiro’s eyes, a leader who benefits selfishly and insincerely off their subordinates is the worst kind of filth- this is a person lower than dirt.
The idea of his identity as a paladin becoming anything consumable, marketed, and thus insincere- offends Shiro’s basic sensibilities about everything why he’s doing this. From the get-go he doesn’t want to perform, he wants to be sincere and straightforwards with people about his ideals and why he needs their assistance.
This is why Shiro, who has been the source of many inspiring, passionate speeches throughout this, and is very charismatic, is an awkward, wooden actor.
I feel like you could draw a fantastic text-to-text parallel with this to Captain America, The First Avenger and how Steve took to being turned into a propaganda machine- going along with it because it ostensibly still accomplished good, but with an increasing sense of frustration and discomfort and going into it clumsy as hell. Because there’s a war going on, and the glamorized view he’s selling is fundamentally insincere to the nature of that conflict.
I mean the specific thing of “now go put on this tight shirt and let a bunch of strangers ogle the physique you developed mostly during a year of being tortured” is probably just icing but I think it also stands that Shiro is, generally, one of the most modestly dressed members of the cast and the most revealing thing we’ve ever seen him in is a sleeveless undershirt. Especially considering that a good part of his trauma is the nagging sense that stuff was done to him, bodily, against his will- I could see the idea of exposing himself being a very touchy subject for Shiro.
And we see Worm Coran (who is… pretty much his own character, quite frankly since real, lucid Coran would not sign off on half of that) pressing uncomfortable roles on the other paladins as well- like when he set out to make Hunk “funny” which Hunk was amenable to assuming he’d be, y’know, cracking jokes himself and not the involuntary butt of a joke, a fantastic thing for a highly intelligent person with anxiety issues and when he’s unveiling his idea for “Shiro the Hero” he maneuvers Shiro’s left arm into a flexing position. Which Shiro also responds very stiffly and very skeptically to.