cliche

Whilst I agree with your main point (that nothing's guaranteed), I think you're overstressing the case; and I think your 'ping-pong vs cargo-net' analogy goes way too far. In actual fact you'd be trusting your life to something more like a 1 in 20,000 chance which is something safer!

From: National Institute of Health report into condom effectiveness for STD prevention

FDA researchers have also developed an assay for condom leakage using high
concentrations of a laboratory virus (78). The laboratory virus penetration assay
is not used routinely as a quality control test, but its sensitivity and relevance are
arguably greater than the conventional water leakage test. Using this virus
assay, FDA scientists tested many different types of male condoms and showed
that condoms are highly effective barriers to virus passage with a very small
chance of leakage (76, 77). Intact condoms (i.e., pass the water leak test) are
essentially impermeable to particles the size of STD pathogens (including the
smallest sexually transmitted virus, hepatitis B). Moreover, these studies show
that fluid flow, not virus size, is the most important determinant of viral passage
through a hole. Even holes many times larger than the virus impeded fluid flow
such that few of the test particles passed through (78).

The methodological strength of the studies on condoms to reduce the risk of
HIV/AIDS transmission far exceeds that for other STDs. There is demonstrated
exposure to HIV/AIDS through sexual intercourse with a regular partner (with an
absence of other HIV/AIDS risk factors). Longitudinal studies of HIV- sexual
partners of HIV+ infected cases allow for the estimation of HIV/AIDS incidence
among condom users and condom non-users. From the two incidence
estimates, consistent condom use decreased the risk of HIV/AIDS transmission
by approximately 85%. These data provide strong evidence for the effectiveness
of condoms for reducing sexually transmitted HIV.

So - yes, you're right - some HIV can get through a condom. But the risks are extremely low - something like 0.6 seroconversions per 100 person-years (usually meaning having sex about 10,000 times). This compares with 6.7 without condoms. So the catholic church is OK to tell people that condoms won't guarantee their safety - but to tell people not to use them is outright dangerous. 'Don't have sex' is defensible, but 'don't use condoms' is just plain frightening.

No, they're not perfect, but they're the best thing we've got. And unless the catholic church is doing this to

__________________
I can't understand why people are frightened of new ideas. I'm frightened of the old ones. -- John Cage (1912 - 1992)