Marshall and the club's co-captains, Api Koroisau and Jarome Luai, fronted media on Thursday following days of turmoil stemming from Galvin's decision to not renew his contract with the club beyond 2026.
Galvin's manager, Isaac Moses, who is at loggerheads with Marshall, didn't even entertain a five-year offer the club put on the table.
It was widely reported that Galvin's dissatisfaction with Marshall's coaching was a major reason he didn't want a new deal, which sparked a chain of events that led to the 19-year-old being dropped for Easter Monday's clash with Parramatta.
"He is our coach, and at the end of the day (if) you disrespect him you disrespect us as a team, and I don't stand for that," Luai said on Thursday.
Galvin was met with ridicule, with both winger Sunia Turuva and Luai taking veiled digs at the playmaker on their personal Instagram accounts.
That led to claims that the teenager was being bullied - a suggestion Marshall rejected.
"I don't think he's being bullied by the other players," the coach said.
"We don't stand for bullying, and I spoke to the team this morning about it - that's not us.
"We're not bullies, our players are not bullies. They had an emotional reaction ... but it's not bullying.
"I don't think (Turuva) should have done it ... but am I going to slap (him) on the wrist for it? No, we don't need that."
Marshall said he was surprised to hear criticism of his coaching, particularly as a premiership-winning five-eighth.
Under his guidance, Galvin enjoyed a breakout season in the NRL last year and was named in the Prime Minister's XIII.
"I was shocked by it and a little bit disappointed," Marshall said.
"Everyone thinks I can't coach anyway, so it's not that different to what's been said."
