I was interested to read that CCFON (Christian Concern for our Nation) are organising a Not Ashamed campaign. On the first of December, CCFON urges us all to don T-shirts proclaiming our Christian faith for the benefit of all the heathens...
I'm not even remotely ashamed of being a Christian, but I would definitely be ashamed to be associated with CCFON! I also wonder whether I'd be a bit ashamed of proclaiming my faith on a T shirt, with the danger that others might think that I was suggesting that I am somehow better, more worthy, holier than others.
I am not sure hard line proselytizing works; I think it is more likely to alienate those who see Christians as judgemental, self righteous, or just plain weird. When people get to know you and learn that you genuinely respect them, then they sometimes open up to you about faith.
I might just be puerile, but I am amused by T shirts with slogans such as, "I've found Jesus - he's behind the sofa!" On the other hand, a T-shirt starkly proclaiming your faith to all and sundry, might just get you a seat all to yourself on the bus ride to work on a Monday morning.