An Evangelical Protestant Perspective:
Summary answer: Yes - there are such things as 'false Christians' (and also 'Inconsistent Christians').
Evangelicals believe that a true Christian is someone who has been 'born again'. It is not membership in a visible church or baptism that defines them as a true Christian, but that they have heard the message of the Gospel, and responded to it (with the necessary enablement of the Holy Spirit) in faith and repentance and have therefore become members of the true Universal and Invisible Church. Adhering to the teaching of Christ and the Apostles is seen as evidence of true faith and repentance ('by their fruit you shall know them'). While there may be some accoutrements of Evangelical praxis that could be construed as official recognition of who is a Christian - such as baptism or church membership - the general understanding is that these are symbols (that may possibly be falsely applied) not the substance that matters. In one sense, this complicates matters in discerning who is a 'true' Christian - only God truly knows who are His - but some level of discernment is possible regarding 'is this person's conduct consistent with their professed faith.'
While this perspective is of more recent origin historically (although adherants would argue it is a return to New Testament Christianity) and may have had less opportunity to generate the egregious inconsistancies the question alludes to, Evangelicals would still recognize that members in their congregation can still fall in to one of two relevant categories: 1. The fallen brother*. & 2. The false brother:
The fallen brother is one who disobeys the commandments** not because they aren't a Christian, but because they (like Eve before them) have been tempted and deceived to do so against their (new) nature (that they would be still influenced by their persistant old nature is a recognised problem also). Their disobedience may range from what outsiders may think the trivial (Peter's denial of Christ) to particularly scandalous (David's adultery and murder), that they remain brothers and have merely fallen is evidenced by a later willingness to repent - acknowledging their error, renouncing it and an evidential re-commitment to the way of righteousness (living by faith - evidenced in obedience to the perfect law of God). This may mitigate somewhat their evil actions, but it is recognised that because of them, 'the name of the Lord is blasphemed'.
The false brother is not a true Christian, but is not immediately discernible as such - they are 'wolves in sheeps clothing'. They have adopted the outward symbols of Christianity and adhere to a bare minimum of commandments that enable them to blend in amongst the Christians that surround them while their heart remains un-regenerated. They may be completely deceived themselves in thinking they are born again, or cunning dissimulators hiding ulterior motives. While the false brother's animus is normally directed inwards at disrupting the work of the Church (particularly by assuming offices of power that they are not called to and becoming false shepherds/teachers/prophets), in certain levels of concentration and sociological conditions, the false brothers may band together and 'break out' against outsiders satiating an innate blood-lust in a despicable fashion (e.g.).
While both may engage in commandment breaking, they may be differentiated to some degree by the former's subsequent humble willingness to confess their wrong-doing and repent of it, versus the latter's prideful self-justification and refusal to repent upon confrontation.
Regarding excommunication, this tends to be rare but not entirely unheard of in evangelical congregations, it is far more common that upon confrontation, the fallen brother will repent before being 'put out', and the pride of the false brother will lead him to decamp before similar action is taken (cf. 1 John 2:19) - excommunication is not usually declared in absentia. Where it is done, it does tend to be for reasons of unrepentant immorality and not (for example) just for maintaining contrary doctrines. Unfortunately (in my view) a common practice is to add the extra-biblical step of asking the person to leave the congregation quietly - usually enacted after they remain unrepentant after confrontation by elders and show no evidence of wanting to leave of their own accord, rather than pursueing the final (biblical) step of (public) congregational/denominational confrontation - the intention is to reduce scandal, but in the long run this practice may perhaps add to it (as well as resulting in less repentance).
*the word is meant in a gender-inclusive sense - my apologies if there is a better term that would actually convey this meaning and still fit the argument appropriately, but none spring to mind.
**Regarding 1 John 2:4 that you've cited, the consistent context of 1 John (and also later in the gospel of John) is that the commandment refers to the perfect law of love. In fact John teaches us that, practically speaking, not only can the whole law be distilled into the two great love commands, but that these can be further distilled into the command 'love your brother (as Christ loves you)' - do 'just' this right (this actually necessarily requires you to walk by the Spirit), and everything else will follow, conversely, if you don't do it, you are not walking the straight and narrow road that leads to life, but the broad way that leads to destruction.