I realize this sounds snarky, but I'm just a North American from the middle of that continent...
Who is deemed capable of deciding which political groups to infiltrate? It seems to me that there's a narrow line between manipulating politics the way you want them to go and observing threats.
I agree with you that it is fantastically problematic to infiltrate political groups.
In theory all of them get scrutiny.
The UK has had considerable trouble with things like employers compiling blacklists of political activists and union activists in order to deny them employment.
Some of the police infiltration scandals have been bad - police either get converted and refuse to provide evidence (while still being paid to gather evidence) or they encourage law breaking amongst legal groups.
I can understand monitoring all political groups (although I don't agree with it) but the UK does this poorly.
Who is deemed capable of deciding which political groups to infiltrate? It seems to me that there's a narrow line between manipulating politics the way you want them to go and observing threats.