Nobody says we're treating particle physicists like "priests"
Whilst I agree with your comment in general, you're about a week behind the times on that one.
1. As you accelerate toward the speed of light (so-called "relativistic" speed), your mass approaches infinity. You reach a point where you can't generate enough reaction to "push" the ship any faster.
Incorrect. You can always push the ship faster because the relativistic mass never reaches infinity, it just asymptotically approaches is. Yes, it gets harder to accelerate the ship, but at no point does it become theoretically impossible.
Time passes more slowly for *you* on that ship, but that's not much help to the people back on Earth who are waiting to hear from you.
Indeed. As I pointed out. Just because I won't be able to tell people about it doesn't mean I wouldn't want to go!
2. Bussard ramjets, which theoretically scoop up interstellar hydrogen for a fusion drive have another problem. First, no rocket can accelerate faster than its exhaust. Second, physicists have worked out the math and even if you could make the "scoop" as perfect as possible, the drag of collecting interstellar hydrogen itself places a top limit on your speed (about 1/2C, as I recall, but I could be wrong). 3. At higher speeds, minor things like cosmic rays and solar wind become lethal particles. (This is being discussed right now as a real problem for a simple Mars mission -- spending a year in space could result in the astronauts glowing in the dark before they get back to Earth!) Ergo, you'll need better shielding.
I never suggested Bussard ramjets, but you're right, they're certainly not the great solution that some SF paints them as. What I had in mind was some variation on a particle accelerator as a drive, that way you can pump relativistic energy into, for example, single protons and use those to give the ship an arbitrarily large push (using Orion Project style shock absorbers to smooth the ride out), this way you get the maximum thrust for a given amount of fuel, you just need a silly amount of energy to do it. With current or near future technology this energy source is likely to be fusion reactors, and as we'd be using a form of water as the fuel for the reactor and possibly as a source of reaction material this becomes a realistic material to use as radiation/high energy particle shielding.
If I had to design a starship I'd start with an asteroid.
A computer scientist is someone who fixes things that aren't broken.