As one can see the issue is the bullets are not maintaining an indent. 
MWE as seen below
\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{indentfirst}
\usepackage{caption}
\usepackage{subcaption}
\newcommand{\tabitem}{~~\llap{\textbullet}~~}
\begin{document}
\begin{table}
\centering
\begin{tabular}{| p{7cm} | p{7cm} |}
\hline
\multicolumn{2}{|c|}{Bezier Curves} \\
\hline
\multicolumn{1}{|c|}{Properties} & \multicolumn{1}{c|}{Disadvantages} \\
\hline
\tabitem A\newline
\tabitem B\newline
\tabitem C\newline
\tabitem D \newline &
\tabitem E\newline
\tabitem F\newline
\tabitem G\\
\hline
\end{tabular}
\end{table}
\end{document}



\newcommand{\tabitem}{\textbullet~~}gives what you looking for. – Zarko Mar 14 '17 at 23:37