Q:

Is "has made it his business to" polite or impolite?

In this sentence:

He has made it his business to reintroduce the theory to a new
  generation of activists.

Is "has made it his business to" an impolite expression?
Is it a radical expression?
Has it any implicit meaning that he reintroduces the theory, but he shouldn't do it?

EDIT: These answers confused me, First sentence of Source article may help better understanding this expression in the context.

A:

All it does is to emphasise that someone has gone about something in a very businesslike way, with determination.
It is neither polite nor impolite. And it is not a radical expression. But it is often spoken with irony e.g. emphasising a business-like way of dealing with something that is not normally a business matter, in order to get over the idea of a determined approach.  e.g. 'They made it their business to make me feel (un)welcome.'
Here are a few further typical expressions:
'I shall make it my business to help the new family settle in as smoothly as possible'.
' I shall make it my business to ensure that his request is turned down'.
'I shall make it my business to find out as much as possible about that company'.
'He made it his business to be as offensive as possible'
'She made it her business to be as helpful as possible'.
These examples simply mean that the person concerned took personal responsibility (i.e. his or her business - no one else's) to ensure that something happened.

A:

To make [a task] one's business is to devote oneself to the task, and treat it as a priority. There is often an implication that the person is taking on a task that no one else is willing or able to do:

When I saw what state the club's books were in, I made it my business to ensure that all of the accounts balanced correctly.

Depending on the context, this may be a welcome and necessary activity, or it may be seen as presumptuous. You should not automatically assume that the use of "made it his business" indicates that the person is acting impolitely; you must figure that out from context.

