It means they've gone too far.
1	It	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	2	nsubj	2:nsubj	_
2	means	mean	VERB	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	0	root	0:root	_
3-4	they've	_	_	_	_	_	_	_	_
3	they	they	PRON	PRP	Case=Nom|Number=Plur|Person=3|PronType=Prs	5	nsubj	5:nsubj	_
4	've	have	AUX	VBP	Mood=Ind|Number=Plur|Person=3|Tense=Pres|VerbForm=Fin	5	aux	5:aux	_
5	gone	go	VERB	VBN	Tense=Past|VerbForm=Part	2	ccomp	2:ccomp	_
6	too	too	ADV	RB	_	7	advmod	7:advmod	_
7	far	far	ADV	RB	Degree=Pos	5	advmod	5:advmod	SpaceAfter=No
8	.	.	PUNCT	.	_	2	punct	2:punct	_
