New pipe smoker, an aromatic tobacco, and new pipe will all contribute to a hot pipe.
1. You are a new pipe smoker, and will by nature be agressive with the pipe, trying to taste the flavor. Slow down, try sipping on the pipe instead of puffing.
2. As said before, aromatics, and in particular Mac Barens will tend to burn hot. This is due to a higher moisture content than other tobaccos. Moisture and heat create steam, which will heat up the pipe and burn your tongue. Again, slow it down, and let the tobacco sit out on a paper plate or paper towel for about 1/2 hour before loading your pipe. This will give a chance for the tobacco to dry out a bit.
3. New pipes haven't built up a cake on the inside yet, and you must be extra careful not to create hot spots, and eventually burning a hole through the pipe. Remember, this is wood, and if not "conditioned" properly, will burn just as readily as the tobacco. A cake needs to be built up to absorb some of that heat, and that only comes with time and patience.
You'll get it, just slow down a bit, enjoy the relaxation of it, and take the time to learn technique in loading, smoking, and cleaning. It's worth it!
WWhermit