People today are only aware of the Salvation Army as a charitable organization, but at its roots it is a evangelical protestant organization. They are a separate christian sect, operating its own churchs (which they call corps).

Early on, one of their primary causes was prohibition. That is part of why the rally cry of the Skeleton Army was "Beef, beer and bacca (tobacco)", to contrast the Salvation Army's "Soup, soap, and salvation".

Not only that, but the SA did run things somewhat militarily. Military rank and titles were used, and they had their "soldiers" wear uniforms (which differ based on what they do, and where they are from). It can be somewhat disconcerting to see people marching around town in uniform, pestering people trying to go into pubs, or anyone else they deem being immoral.

Add into this how quickly the Salvation Army grew. It originally was a small church, but just two years after adopting the name Salvation Army, they were operating in 4 countries. Their first convert in the US was actually someone who was ordered by a judge to join.

Part of the reasoning for Wells dislike for the Salvation Army deals with the response to his book "In the Days of the Comet". The book ends with the main characters being in a polyamorous relationship, instead of just two separate marriages. The Salvation Army came out against this, as it clashed with their belief of traditional marriage.

So, with all this in mind, it isn't difficult to understand why Wells would take issue. This was a rapidly expanding theological organization that pushes its beliefs while in uniform and behaving like a military, and taking advantage of legal force when possible.