How can I really force the hyphenation points of a word?

\hspace{0pt} right before Sicherheitsbeauftragter allows TeX to break the word, because TeX does not hyphenate the first word in a paragraph. (AFAIK this had made the implementation easier and in English with the many short words, it wasn't much of a problem.)

Since the \hspace inserts a break point at this place, this can be avoided by \nobreak in horizontal mode:

\leavevmode\nobreak\hspace{0pt}Sicherheitsbeauftragter

Or the star form of \hspace can be used:

\hspace*{0pt}Sicherheitsbeauftragter

This can be automated (see Herbert's comment) in the column description:

\begin{tabular}{>{\RaggedRight\hspace*{0pt}}p{7.7em}@{|}}

You can also suggest places for hyphenation using \-. The following works for me.

\documentclass{article}
\usepackage{polyglossia}
\setmainlanguage{german}
\usepackage{array}
\usepackage{ragged2e}
\begin{document}
\begin{tabular}{>{\RaggedRight}p{7.7em}@{|}}
Sicherheits\-be\-auf\-tragter\\
Technischer Leiter
\end{tabular}
\end{document}