A rational person would have taken the free Enron stock, but used their own contribution on more conservative investments.
It isn't speculative at all.
A match is a match - the same nominal dollar amount of equity for every dollar of cash contributed by the plan owner.
Everyone knows that a single stock is riskier and more volatile than a diversified portfolio of similar stocks. Everyone also knows that a value stock is less volatile than a growth stock.
Therefore it is not speculative to say that if your motivation is preservation of your investment over a short time horizon, it is a financially sound decision to invest in a diversified portfolio of value stocks as opposed to putting all your money in a single growth stock.