Is it true that high cholesterol contributes to impotency?

Yes: High cholesterol is a risk factor for endothelial disease which is the vascular mechanism for both coronary disease and impotence.

LDL, not Cholesterol: Cholesterol is a fat molecule manufactured by every animal cell, a building block of each cell membrane (enables membrane fluidity/movement without tearing), is fundamental to the survival of every animal cell. Lipoproteins (proteins which transport all fats in the water outside cells) is the correct issue for artery disease (e.g. Ldl ≤700 nmol/l, HDL ≥45 µmol/l). Cholesterol ↓$, but misleading.

It can: If plaque build up restricts blood flow.