Adding to what bill_o said, bonds, and especially government ones like munis, stand to lose a large proportion of their value as soon as interest rates increase.
Your friend the old-timer probably owns municipal bonds from the good-old-days, e.g. they were issued when interest rates were high, and therefore are still paying out pretty well and even increasing in value apart from dividend payments. Still, YOU can't get those bonds, and when interest rates increase again, your friend the old-timer will also see a hit to the market value of his bonds.
Long story short: It's really the wrong time for bonds. Honestly, with an investing time horizon of 5-10 years, you're safer investing in index funds.
While this is generally true, the specifics make all the difference.
If you buy a municipal bond and hold it to maturity then there is no direct interest rate risk. The risk is in owning a muni bond fund. In that case you can look at the duration and know how much the price will decline if rates rise. A typical muni fund at one of the firms usually mentioned here has duration of less than 5 years. If rates rise like crazy to their historical norm they will go up about 2%. The Fed is saying that will not happen for at least 2 years. If anything the Fed is trying to figure out how to push real rates further down. But if they do rise back to the norm over 2 years then those muni funds will go down about 10% over the next few years. My index funds lost almost that much in May! So saying you will lose a "large proportion" of your investment is an exaggeration.
I have always avoided muni funds for a different reason - they market supposedly prices them so that they pay the same yield as corporate bonds after adjusting for taxes in the highest tax bracket. That's the theory at least. But over the last decade the actual result has been that they have yielded the same as equivalent taxable bonds for people in about a 20-25% tax bracket. Since we are in a higher bracket we have started buying muni bond funds with some of our bond investments because the math seems to make sense.
I agree that right now is not a good time for bonds. But our reason has to do with allocation not timing.
I also agree that munis should never, ever be put in an IRA or Roth and also don't see how the conversion has anything to do with this.