This entry is not meant to convince anyone of the virtues of humanism itself, or to argue that this or that religion is not the case; these points are taken for granted here. I am instead trying to make the case to humanists, who agree with me on the aforementioned already, that there is something to be gained by an evangelical approach. With the scope of my intentions established, let us begin in earnest.
So, why evangelical humanism? In short, because the world needs it. At length, I believe that humanism is the best system of belief for the future of humanity, and must replace supernaturalistic religion as the dominant cultural meme in the near geological future if we are to survive as a species and make lasting social improvements.
Evangelism is, put simply, a charismatic approach to espousing an idea. There's nothing wrong with evangelizing in and of itself - what is being evangelized (and why) is more important by far. For example, when global warming threatens the vast majority of life on Earth, an evangelical approach may be called for, in order to spread the word and encourage constructive change in those habits of ours which affect the climate, all in the name of good solid science and the long-term interest of life in general. As Penn Jillette says in the Penn & Teller: Bullshit! episode on the Bible, "The fact is, we are two evangelical assholes. Bullshit is an evangelical show. TV preachers are doing exactly the same thing we are doing - they are telling the truth as they see it." In other words, there is nothing wrong in principle with putting one's point of view out into the marketplace of ideas, for all to see, with the intention of convincing others of that point of view.
Contrary to the popular association of evangelism with Christianity, evangelism has nothing to do with Christianity, neither by necessity, nor by rights. Jesus Christ himself explicitly directed his followers to eschew public prayer and pious displays, and instead to keep their faith to themselves as a private matter between them and their god (Matthew 6:5-7). This is good advice, and I am rather disappointed that so many appear not to have taken it to heart. Supernatural claims are categorically unknowable, in that they are unverifiable and unfalsifiable matters of faith. Leaving aside the fact that empirical study can render them superfluous, there simply is no way to settle such matters (especially not between competing supernatural claims, as they're all equally ridiculous).
Humanism, on the other hand, is a philosophy centered around human life on Earth. It is concerned with the improvement of people, at both the individual and social level, and lacks the focus on the hereafter which is typical of religions. This focus has given religion tremendous memetic survival value in the past, by trading people hope for a better life after death, in exchange for patiently enduring misery in this life. But, lacking any possibility of verification, claims about a life after death are unactionable wishful thinking which lull their adherents into complacency, and in modern times these claims at best serve only to distract us from those issues which truly do deserve our attention. At worst, they actively encourage us to look forward happily to the destruction of the world, an event which we have only recently gained the capability to cause.
The belief that there is a second, eternal life is a distraction from this one for reasons of pragmatic mathematics alone: compared to eternity, a century or less vanishes to nothingness. What importance can this life have, aside from the question of picking the right religion to ensure one's eternal bliss after death? Even taking into account the actual suffering that happens on Earth, which we know to occur, the belief in an afterlife can only dismiss Earthly matters as ultimately unimportant, and this is perhaps the most terrible mistake we can make: to not care about the real and important concerns facing us here and now, in favor of a hope for things unseen (Buddhism is a rather remarkable exception to this rule, but that is a subject for another day and I shall leave it for now with but a mention). Humanism is the antithesis of this position, dismissing those matters about which no knowledge may be gained in order to place our focus properly upon those matters on which we can gain knowledge and make improvements. And because there is actionable content and purpose in the belief system, evangelizing for it is not an empty exercise as it is for religion, but instead a legitimately useful activity.
Evangelizing for the humanist worldview, far from being the pointless exercise of spreading ancient myths, is perhaps one of the most culturally impacting actions that can be taken by any everyday citizen at this point in history. Looking at the data, we see that the least religious nations tend to be the best nations for their citizens - and every citizen plays a role in shaping that trend. Living by example, we can show that a secular humanist lifestyle is a better way than that of superstitious piety. We can spread the word of science, embody the virtues of empathy and inclusion, preach the good news of secular democracy. We do this not to save souls, but to improve standards of living by encouraging others to work for a better life here, rather than preparing in vain for another life we cannot justifiably expect. Living our lives according to these values, and encouraging them in others, is an investment in long-term cultural change which we would be wise to make.